64 HYDROIDvE. 



tenth of an inch in height, the arrangement of the tentacles is totally 

 different from that of the adult. They are as yet not arranged in clus- 

 ters, but placed at regular intervals in one line on the edge of the disk. 

 No difference can at present be detected between the anchors (a, Fig. 

 90) and the tentacles (t, Fig. 90) of the disk, showing plainly that the 

 anchors, as Professor Clark has proved, are only modified tentacles ; the 

 peduncle is also quite short, and stout in proportion to the disk. The 

 young Lucernaria is in this state a close representative of the genus 

 Carduella of Allman, which may possibly prove to be only the young 

 of some European species. 



Greenland (Steenstrup) ; Anticosti (Verrill, Shaler, and Hyatt) ; 

 Massachusetts Bay (H. J. Clark). 



Cat. No. 320, Naliant, Mass., A. Agassiz, May, 1862. 



Cat. No. 321, Chelsea Beach, L. Agassiz. 



Cat, No. 322, Mount Desert Islands, Maine, W. Stimpson. 



Cat. No. 323, Anticosti Island, Anticosti Expedition, August, 1861. 



Cat. No. 380, Anticosti Island, Anticosti Expedition, August, 1861. 



Haliclystus salpinx H. J. CLARK. 



Haliclystus salpinx H. J. CLARK. Journ. Bost. Soc. Nat. Hist., p. 563. 1863. 



Mount Desert Islands, Maine (Stimpson). 



ORDER HYDROID^E JOHNST. 



Anthozoa Hydroida JOHNST. Brit. Zooph., Second Edition, p. 5. 



Gymnophthalma FORBES. Brit. Naked-eyed Medusas. 1848. 



Coralliaria Tabulata, Ititf/osa, and Hydraria MILXE EDW. & HAIME. 



Hydromedusce et Siphonophorce VOGT. Siph. de Nice. 



Hydroidea, Medusida Craspedota, and Siphonophora GEGENB. Zeit. f. W. Zool. 1856. 



Hydroidts McCR. (p.p.}. Proc. Elliot Soc. 1857. 



Jf//i/rozoa HUXL. Ray Soc. 1859. 



Hydroidce AGASS. Cont. Nat. Hist. U. S., III. 1860. IV. p. 337. 



From want of materials, no writer on Acalephs has thus far attempted 

 to make use of the embryological characters noticed in the development 

 of young Hydroid MedusaB and of the young Hydraria. From the ob- 

 servations of Wright on the development of Thawnantias inconspicua, 

 of yEquorea, and from what I have had occasion to observe myself on 

 the Hydroid of Melicertum and of Tima, we have acquired sufficient 

 information to satisfy ourselves that Tubularian-like Hydroids stand 

 lower than the Campanularians ; while such forms as the Hydroids of 



