G6 



INVEFTEBBATE ANIMALS. 



Hijdrozoa. The sjieeial elements of rejiroduction are developed in 

 these detuched buds, but the resulting embryos are not developed 

 into Mednsce, such as produce the ova and sperm-cells, but straight- 

 way gi'ow up into the jjlant-like sexless colony, from which the 

 rnedusiform gouophores were originally budded forth. In these 

 cases, tlierefore, the individual Hydroid consists of a fixed, rooted 

 colony (or trophosome), producing fresh zooids by a process of bud- 

 ding, but incapable of producing the essential elements of reproduc- 

 tion, together with a free and independent series of generative buds 

 (or gonosome), in wliich the elements of rejiroduction are developed. 



Order III. SERTUL.iRiDA. 



In this order of the Hydroida we have the most familiar and 

 best known of all our zoojihytes — namel}', the Sea-firs and their 

 allies. The horny jilant-like polyparies of the Sertvlarida are 



Fig 34. — a N''/7('/y; ;// {rZ/p/ffrs/'fl) pUrnnfa, iiatnr.i] size; a' Fra;:;ninnt of the same en- 

 larged, canyjjig ii mull' c-qisulr (.,), uml slinwiiig tlie hy.lr.itlieciv (A) ; b Fragment 

 i,iL;iini„i,ni}:i,in ,u,jhrl„ (after lliTLik^), sle.wing (lie lioly|iile"i oontaine.l in tlleir 

 ]i\-'ir(ptlirr;,- (A), ninl alsii the iii'int at wliicli tin; e(i.-in>.sare cuinninnicates with the 

 stuinaeli c,]' i),i. pnlyi.ite- (e). 



familiar to every visitor at the sea-side, ami by those unacquainted 

 witli tlieii' true natin'e they are .almost universally set down as sea- 

 weeds, "^riie SertidKridii are very closely allied to the compound 

 fMriiis of the Ciiri/iiiiht, resendiling them in being rooted, plant-like 

 cull. 111. s, I aimposed of M, number of simil.ir polypites or zooids, pro- 

 duced liy budding from a (irimitive zooiil. As in the Tubularians 



