NO. 1302. AMERICAN PA RASITIC ARG ULID.E- WILSON. 671 



best one possessed by the larva. In confirmation of such a view, wit- 

 ness 'the fact that in several of ourjaro-est species {nigeT^ cato.sttnni, 

 etc.) the abdomen is proportionally very small, in ratosfomi so diminu- 

 tive compared with the enormous head-thorax that it could not possi- 

 bly keep the blood aerated. 



The nervous system consists of a '" t)rain," which is situated near the 

 dorsal surface of the carapace just above the mouth and just beneath 

 the unpaired eye, and a chain of ventral ganglia (Plate VIII, tig. 24). Of 

 the latter the two anterior ones lie close to the mouth on the ventral 

 surface and the four posterior ones lie beneath the stomach, and are 

 so hidden by its opaque contents as to be visible only during con- 

 tractions. 



On the ventral surface of the brain on either side may be seen a small 

 swelling, the beginning of the mouth commissure, which in later devel- 

 opment surrounds the mouth and 1)inds the biaiii to the anterior 

 ventral ganglion. 



Alongside the anterior liorder of the side hiiiiichos of the stomach, 

 well out toward the edge of the <ara])a(t'. may )»(' seen the paired shell 

 glands first detected by Chius in the /^/A/r, us larva. As will be seen 

 on Plate VIII, they can be distinguished by the si/e and grouping- of 

 the cells. The walls are two-layered, and at the anterior corners may 

 be seen the lumen of the duct. 



In none of the larvte is there visil)le anything, even imder an oil- 

 innnersion lens, which can l)e definitely asserted to \w th(> beginning of 

 the asynuuetrieal ovary. And yet there are many reasons for believing 

 with Claus that careful sectioning will re\('al the rudiments of an ovary 

 in all these larvte. 



He discovered it just after the first molt considerably developed and 

 reasoned that it must have Ixhmi present ))efore. 



But if this were true in follm; us and <-ufi>sii>ni!, there is, of course, 

 more reason for suspecting it in the nmeli better develop(Hl larva^ of 

 niK/iilops 'A\\(\ sf host, flu!. The probalnlity of its exist(>ne(Ms gi-eatly 

 strengthened by the fact that all the other reproductive organs in both 

 sexes are present and plainh^ visible. The seminal pouches in the 

 female consist of small, inversely |)eai'-shaped liodies jjlaced just inside 

 the row of glands close to the base of the abdomen (x. y.. Plate Mil). 

 The ducts from these glands and the papilla' on the ventral surface 

 with which they are connected are not yet developed. 



The testes in the abdomen of the male are much huger than these 

 seminal pouches of the female and show the beginnings of a central 

 lumen (/., fig. 9). They correspond in position with the pouches and 

 at their upper ends may be detccte(i the 1)eginnings of the vasa^ effer- 

 entia\ None of the accessoi'v copulatory organs are ])i'esent on the 

 legs of the male at this stage. 



As soon as they emerge from the egg, therefore, the sex of the 

 larvffi can be determined with certaintN'. 



