INTRODUCTION. \ \ I 



the Thecaphora, these reproductive buds are always borne 

 on an offshoot from the ccenosarc, which is enclosed in a 

 chitinous receptacle or urn (gonothcca) . (Woodcut, fig. 

 xv.) In the suborder Athecata they are never protected 

 by a true gonothcca,, though in sonic species they are 

 encased in a thin coating of chitiue. In this division they 

 occupy very various positions. Sometimes they are deve- 

 loped irregularly amongst the tentacles of the ordinary 

 polypite (Coryne), or at different points on the body (Cla- 

 vatella and Podocoryne) ; in other cases they occur on 

 the cosnosarc (Periyonimus) , while in Tubularia and its 

 allies they germinate at the base of the lower circle of 

 tentacles. In other cases, again, they are borne on special 

 zooids, which are evidently polypites more or less atro- 

 phied and deprived of some of their characteristic parts. 

 The atrophy varies in degree : sometimes it shows itself 

 in a reduction of the number of tentacles ; sometimes these 

 organs are represented by mere clusters of thread-cells 

 (Hydr actinia); sometimes they are altogether wanting 

 (Cionistes], and the polypites become nothing more than 

 a columnar offshoot from the coenosarc, closely resembling 

 that which bears the gonophores within the capsule of the 

 Thecaphora. The zooid (whether modified or not) which 

 carries the reproductive buds may be designated the fertile 

 or proliferous polypite *. 



In Hydra the reproductive buds are developed within 

 definite regions on the body of the polypite, and are gene- 

 rally produced when the ordinary gemmation has altogether 

 ceased, or is beginning to fail, (Woodcut, fig. 40, p. 313). 



The gouophores exhibit many modifications; like the 



* The modified polypites whose function it is to originate the sexual buds, 

 and which take no part in the nutrition of the colony, are the c/onoblast'uliu 

 of Huxley. 



