Proceedings of the American Academy of Arts and Sciences. VOL. XLII. No. 18.- JANUARY, 1907. CONTRIBUTIONS FROM THE ZOÖLOGICAL LABORATORY, SYRACUSE UNIVERSITY; ALSO CONTRIBUTIONS FROM THE BERMUDA BIOLOGICAL STATION FOR RESEARCH.No. 9. THE HYDROIDS OF BERMUDA. BY EDGAR DAVIDSON CONGDON. THE HYDROIDS OF BERMUDA.1 EDGAR DAVIDSON CONGDON. Presented by E. L. Mark, November 14, 1906. Received November 2, 1906. THIS paper has for its purpose the description of certain hydroids which I collected in the summer of 1903, while an attendant at the Bermuda Biological Station. They were investigated under the guidance of Dr. C. W. Hargitt in the Zoological Laboratory of Syracuse University. I wish to express my great indebtedness to Dr. Hargitt for his suggestions and criticisms, and to thank the Bermuda Biological Station for courtesies extended to me during the season. Verrill ('99, p. 571) has stated in the Proceedings of the Connecticut Academy of Science that eleven hydroids occur at Bermuda, but he does not name or describe them. I know of no other zoologist who has occupied himself with the subject. Of the eighteen species that were found, eight were previously undescribed. Each species which had been previously described varied in some small degree from the type individuals. The various common hydroid families are quite equally represented. Eudendrium hargitti, a new species, is especially interesting because of phenomena of oögenesis which have been elsewhere described (Congdon, :06). Two new species of Halecium present female gonophores whose structures are significant when compared with the gonophores of other species of the genus. Few hydroids are found on the exposed southern shore of the Bermudas. The coves, inlets, and reefs of the opposite shore are well supplied with individuals and species. The Sargassum, which floats in after a prolonged south wind, often is the home of an abundance of Aglaophenia minuta, Halecium, and Clytia simplex. Pennaria tiarella, Eudendrium ramosum, Sertularia humilis, and Sertularella brevicyathus are the most common species. E. hargitti, Sertularella speciosa, and Thyroscyphus intermedius are each confined to some single very restricted locality. In the few places especially favorable to hydroid life the strife for foothold is so marked that seven of the small species may be found growing on the larger ones. 1 Contributions from The Zoological Laboratory, Syracuse University; also Contributions from the Bermuda Biological Station for Research, No. 9. The Bermuda hydroids show a close relationship to those of the West Indies and the Gulf of Mexico. All the genera of the new species and all but one of the species previously described are there represented. The remaining species, Bimeria humilis, has not to my knowledge been found south of New England. FIGURE 1. Colony of Eudendrium hargitti (×10). GENUS PENNARIA McCrady. Pennaria tiarella McCrady. The Pennaria tiarella of Bermuda has on the average three more filiform tentacles than that of Wood's Hole, Mass. Clarke ('79) described a member of this genus from Cuba, under the name of P. symmetrica, in which the gonosome was lacking. The characters which he considers specifically distinctive are: the exact form of the hydranth, the origin of the tentacles from a little above the base, and the presence of eighteen filiform tentacles. The first two characters vary greatly with age and the amount of food in the hydranth. The number of tentacles does not seem to me of specific importance, because it varies considerably, owing only in part, I think, to the degree of maturity. It seems probable that P. symmetrica, like the Bermuda form, is a geographical variety of P. tiarella. GENUS EUDENDRIUM Ehrenberg (in part), 1832. Eudendrium ramosum Linnaeus. E. ramosum differs in three respects from the individuals of Wood's Hole, Mass. There is a slightly larger average number of tentacles; there may be one more lobe to the male gonophore ; the hydranth to which the clusters are attached is often entirely aborted. Eudendrium hargitti (new species). Figures 1-5. This hydroid was found at only one place, a shallow inlet on the south shore of Bermuda (lat. 32° 16′ 50′′", long. 64° 45′ 5′′). It is a handsome little form with bright reddish brown hydranths and horny brown perisarc, which contrasts with the usual substratum of white coral sand (Figure 1). Trophosome. Stem unfascicled; colony twenty to fifty millimeters long, becoming nearly transparent toward the extremities. Branches straight, few, nearly par allel to the main stem, distributed irregularly, joining stem by an abrupt bend. Annulations at bases of colony and branches, occasionally elsewhere. Hydranth most deeply colored at base of hypostome; tentacles from thirty-five to forty-five, in contraction forming two closely appressed rows; hypostome very mobile, contracting into a shallow cup or extending to a length greater than that of the hydranth body. Some hydranths provided FIGURE 2. Eudendrium hargitti. Orthospadi with a groove near the ceous and streptospadiceous gonophores (× 11). base containing gland cells and thread cells. Female Gonosome. Colonies dioecius. Two types of orange-colored gonophores (Figures 2, 4). One begins its development before the other, has an undivided. spadix, consisting of a tube passing from the attachment upward and around the egg, and forms in conjunction with not more than four others a circle around the base of the hydranth body. The gonosomes of the second type are associated in clusters of two to seven closely and rather irregularly around a thick finely annulated pedicel, which may or may not have a terminal hydranth. They are partly confluent with the stem, ovoid, completely invested on the exposed side by a spadix, often indistinctly separated into a proximal and a distal group. A dozen clusters may occur close together on a basal VOL. XLII.-30 |