No. 8. ON TURRITOPSIS NUTRICULA (McCRADY). 



BY WILLIAM KEITH BROOKS AND SAMUEL RITTENHOUSE. 



PART 1. THE METAMORPHOSIS OF TURRITOPSIS. 



BY WILLIAM KEITH BROOKS. 



a 



TAI 



(The references in Part 1 are to the illustrations in a memoir on the life-history of the 

 Hydromedusae, which was published by the Boston society of natural history in 

 1886, as volume 3, no. 12, of the Memoirs of the Society.) 



IN a memoir that was written in September, 1885, and published 

 more than twenty-two years ago, I gave a figure, plate 37, of a hydroid 

 cormus of Turritopsis with medusa buds in many stages of develop- 

 ment as well as free medusae at successive stages of growth up to 

 the mature sexual adult. From this memoir I have compiled the 

 following account, in order to point out the more prominent features 

 in the life history (Brooks, '86, p. 391-393). While I have made a few 

 verbal changes and abridgments, the extracts are practically as 

 they were printed in 1886. 



'The only colony of the hydroid which I obtained was scraped 

 from the piles of the steamboat wharf at More head City, seven or 

 eight feet below low tide mark. The tips of two of its branches are 

 shown in H, in PI. 37. It lived for two weeks in the house, and 

 set free great numbers of hardy medusae which were reared until 

 they had acquired the characteristics of the genus." 



The upright stems of the hydra, from 8 mm. to 12 mm. high, 

 bear large terminal hydranths, as well as smaller ones which are 

 scattered irregularly along the stem on short stalks. The long fusi- 

 form body of the hydranth carries from eighteen to twenty thick, 

 short, filiform tentacles, which are arranged in three or more indefi- 

 nite whorls. The medusa-buds, B, B, originate around the stem just 

 below the hydranths, and they are themselves carried on short stems. 

 The perisarc is not annulated, and it forms a loose cylindrical sheath 

 around the main stem and the short branches which carry the lateral 

 hydranths and the young medusae, while the latter are closely in- 

 vested by a much thinner and more transparent capsule of perisarc. 

 The sheath on the stems is thick and crusted with foreign matter. 

 It terminates abruptly by a sharp collar just below each hydranth. 





