HYDRACTINIA ECHINATA. 23 



reference to Plate IV. fig. 6, which represents a young poly- 

 pite in an early stage of growth. Before the formation of 

 the head and tentacles, radical prolongations are given off 

 at the base, which are the beginnings of the stolonic net- 

 work. The spaces between them are gradually filled in by 

 the extension of the coenosarc until they are almost united ; 

 but instead of coalescing, they seem to secrete on each side 

 of them the chitinous lamellae, the spinous ridges of which 

 soon show themselves on the surface * ; and the passages 

 thus formed are covered in by a reticulated roof. The 

 free investing layer of the coenosarc rests upon this roof 

 and conceals it. 



In an early period of growth the base of Hydractinia 

 appears, according to Dr. Wright's observations, under 

 various forms, and, in some of the conditions which he has 

 described, resembles very exactly that of Podocoryne at a 

 corresponding stage. But the development of this portion 

 of the structure requires further investigation. 



H. ECHINATA, Fleming. 



AI.CYONIUM ECHINATUM, Flem. Brit. An. 517. 



ALCYONIDIUM ECHINATUM, Johnst. Br. Z. (1st edit.) 304, pi. xlii. figs. 3, 4. 



HYDRACTINIA LACTEA (the male), Van Sen. Tubulaires, 64, pi. vi. figs. 7-14. 



ROSEA (the female), Van Ben. Tubul. 63, pl.vi. figs. 1-6. 



ECHINOCHORICM CLAviGERUM, Hassall, Ann. N. H. July 1841, 371, pi. x. fig. 5. 

 SYNHYDRA PARASITES, Quatrefages, Ann. Sc. Nat. xx. 232, t. 8, 9. 

 HYDRACTINIA ECHINATA, Johnst. B. Z. 34, pi. i. figs. 4-6 ; T. Strethitt Wright, 



Edinb. New Phil. Journ. (N. S.) for April 1857 ; idem, Ann. 



N. H. for August 1861 ; Allman, Proceed. Eoyal Soc. Ed. 



session 1857-58. 

 ,, FOLYCLINA, Agossiz, N. H. U. S. iv. 227, pi. xvi. (vol. iii.) and 



pi. xxvi. (vol. iv.) fig. 18. 



Plate IV. 

 CHITINOUS CRUST covered with numerous grooved and 



* Vide De Quatrefages on Synhydra, Ann. Sc. Nat, (2nd ser.1 Zool. xx. -M.">. 



