TIIK SKRTI'LARIIi.K. 29 



to pull aside the tissues In make room for a second gonophore. 'I'licv arc composed of liotli 

 ectodermal and endodermal cells, and max be larovlv the disoryani/ed remains of the first 

 gonophore. 



Those who arc familial- with Weismaim's o-rcat work will see that the above account is 

 practically a summary of the results t ,\' his investigations. The present writer, however, has 

 gone over the ground with some care and with yood material and linds that the facts are us 

 described by \\ cismann. The deiliictions arc Li'ivcn on the authority of that writer, unless the 

 context shows them to lie my own. 



Probably the simplest form of o-i phoi-c found in this oroup is illuM rated \,\ /ttji/mxi,! 



kincaidi,a new species described lieyond. In this case thegonophore consists of a st i-nctnrc similar 

 to that of Sertutaria pumila yiven oil'. from the lower p:irt of the blastostyle. It contains, how- 

 cver. hut a single ovum, and in optical section shows very beautifully the relationship lie! ween the 

 ova and the various historical layers, the former beiiiff outside of the stut/lamclle and embedded 

 in the ectoderm (li<j-. x.">). The deckcnplatte is also well shown and is seen to consist of both 

 ectoderm and endoderm. The acrocyst does not appear to lie present iii this species and it is 



probable that the ova are discharged directly through the tops of thegonangia into the water. 



Practically the same type of gonophore is found in S, rtnliiri/i xfonl; ///. .V. i-nrnii-i mi . Itirti/,, 

 rltuli am il<il>, II mil and Tliniiir'ni rnhiixtu. and doubtless in many other species. 



Weisiiiann examined the yonophoivs of S, i-lnlni-. llu /'///:>/// /r/.v and found that they differed 

 from those id' Sertvlaria pumila in the fact that no true gonophores are found, but that the sexual 

 products are developed in the walls of the spadixof the Mastostyle. I found that the same state 

 of affairs was evident in optical section of X r1nl<n-< ll<i <-<>ni/>lf.i-ii. This is shown in fiy. Si!, where 

 the axial blastostyle does not hear jjonophores, hut in which the spermarics are found cndiedded 

 in the endoderm of the blastostyle itself. Numerous thread-like processes extend from the 

 ectoderm of the blastostyle to the o-onano'ial walls, resembling greatly the gubernacula 

 described by Weismann. As there is here no likelihood of an acroeyst beino- formed, the 

 specimen beino; a male yonanyinin. and as there is no cr (m opliore to lie. accommodated, the 

 function of these threads can not be explained as in the case of .V, rtnliiri,i j>niii!l<i. They seem to 

 he a very conmioii feature of the various genera of Sertularida>. and doubtless have a definite 

 significance. In some cases there is a thin layer of ectoderm linino- t he yonanyial walls, and these 

 thread-like structures seem to connect this ectoderm with that of the blastostyle or yonophores 

 in the center of the gonangial cavity. They may, of course, have a nutritive function, as 

 suggested by Weismann in the case of the gubernacula of X, rtuliii'iii juniiilu. In many species 

 of Sertvlarella there seem to be no true gonophores, the ova bcino- in masses around the axial 

 blastostyle. Often they are ayyivyated in two or more distinct o-lobular masses, as in X. n'/i 

 form!* (liy. S"), and some at least of these forms are provided with an acrocyst. as in .V. />/,/, Ml / 

 (Plate XVII, ti<;-. "2). where this structure is very conspicuous. The exact succession of events 

 has not been worked out in such cases, but it is likely that these masses of ova are discharged 

 into the acrocyst just as those in the gonophores of X rtiihtriii pmnilii. the successive masses 

 acting as do the successive gonophores. 



In some species of S, ,/ n/<ir< llu . as .V. i//?i/',/,/. the male yonanu'ium contains an immense mass 

 of sperm cells that is ovate in form. A longitudinal section of this mass shows that it is permeated 

 by a system of divcrticula from the axial blastostyle. These diverticula are apparently composed 

 entirely of endoderm ' covered with the stut/.lamelle, and, I tind no ectoderm save that which 

 forms a coating over the entire sperm mass. This seeni.s to be a form of pseudo-gonophore 

 derived from the condition found in 3. polyzonias by Weismann and in .S'. i-umjili rii by myself. 

 The diverticnla spoken of are probably necessary as a means of conveying nourishment to the 

 mass of sperm cells that is too hi rye to be supplied by a simple unconvoliited endodcrmal layer, 

 such as is found in .S'. ]><ilif::iiiii<ix. If correctly interpreted, we have here a state of affairs almost 



'Tills strurliirr is |inilp;il)ly tlmt whicli is ciiHeil a " Slniin:i-\el/.cs." U'ciMiiann dues not slate Ihe <.rif.'iii 

 of this structure, ami I am l>y no means sure that it is rorrertly intrrpivtcil l>y me :is eiiilncleriual. It ap|icars. 



however, to lie derived directly from the eiidoderm of tin- >|iadi\, and seems to li m posed of loosely ai_"_ r re^atc(l 



tissue, sueli as we oftoii tind in the derkcniilatte, where hoth i-i-to.lenn and eii.loderm arc often of this hjfltological 

 structure. 



