THE SKRTULARID^;. 



27 



the structureless stutzlamelle and greatly enlarged during the growth of the now practically 

 mature gonophore. 



The distal end of tlie latter at this stage is eovered by a distinct layer of perisarc, which has 

 a definite, function presently to be described. It will be noted that only a few of the numerous 

 ova in the blastostyle. arc included in the gonopliorc at this stage. A still further development 

 results in the formation of the acrocyst, a structure found in several groups of calypteroblastic 

 hydroids which consists in a more or less globular body composed of ehitin which surmounts the 

 gonangium and contains the o\ a in their later stages of development. The acrocyst is formed 

 as follow--: The chitinous distal end of the gonophore described above is pressed against the 



84 



83 



80 



THK CJOVOSOMK op SERTl'I.ARIA ITMILA. 



I Kit's. T'.l ami Ml. nfliT Wcisniiinii: I'IKS. M, S'J. ami s:;. nflcr I.. Anassiz.) 



Kin. 7'.i. I,oni,'itiiilitial sTc'liim i>f K'"iiani,'iiiin. ilk. " ili'rkriiplatt.-": .-, mvity uf Konoplion-; iH. ci'to'linn; on/, I'liiloHerm; or. ovum in 



{.Milo'lurm of blastostylr; i'\ OVIUII ill l-rloikTln of t'OIKiph'Ti'. 



KIK. MI. l.oiiu'iliKliiuil M'c-lionof mi ciIiliTKiuniiiKiuni. HIT. urroc-ysl. tiltt, cnvilyof blustostylr; i/uli. milirmHcnliim; other lettering as nn fig. 79. 



Fif. .si. (ivntTiil viciv of fuiiink' Konaiifiiini. i/r, nviim: lilnl, l.lnstostyk'. 



KJL'. SL'. Cciu-ral virw of ni.-ilr K"it."iL,'iiiin. />t*t. hlaslostyli-; >;, spiTinarv. 



Kin. s;:. -iloiiniit'iiiiM. sixiwini; ilivrrtimla from ilcrkrnplntli-. ''. ilivvrticulH. 



Kit'. M. l.onKitmlimil M'c-lioli of part of Ilir >t,-in. -liowilii; .IrvrlophiK ova ill till' ollfldrtcrm. 



deckenplatte by the further u|iward growth of the gonophore. Weisinann' says that this distal 

 end is thrust through a hole or opening in the end of the gonangium. I have, been unable to find 

 such an opening in all cases, and would suggest that the chitinous end of the gonangium may be 

 sometimes pierced by the chitinous end of the gonophore, much as, according to Weisinann's own 

 account, the incipient gonophore pierces the thick perisarc of the stem in Plumvla/ria echinulata 

 by what appears to be a dissolving secretion of some kind. However this may be, the end of the 

 gonophore in some wav penetrates the top of the gonangium and then expands into a globular 

 chitinous sac into which the ova pass, and thus the acrocyst is formed (see tig. Sii, <i<-r}. Those 

 parts of the gonophore that arc not needed in the acrocyst - indeed all parts except the developing 



'Entstehung der Sexoalzellen bei don HydroinrdiiM'ii, isjs:',, ji. 170. 



