Ö7S T. IKEDA : 



to the so-called nnal ridge on tlie dorsal side. Thus we see in fig. 

 00, wliieh sliows a transverse section tlirough the nephridial region 

 of a completely metamorphosed larva of type A, that the tv\'o 

 nephridial canals {nep.c.) are situated very close to the intestine 

 {int.) which lies in the dorsal median line, and that one of them 

 (the right in the ligure) opens to the exterior. By examining 

 serial sections it was found that the excretory cells wei-e entirely 

 al)sent on the nephridial canals, and that the latter were of an 

 inconsideraltle length, ending hlindly at the inner extrennties. Tl 

 seems verv jn'ohable, as was ])ointed out 1)y Caldwell, that the 

 excretory cells of the larval n('])hridia are thrown off into the hody- 

 cavity ; it is also probable that that ]M)rtion of the nephridial canal, 

 which lies in the collar cavity of ArUnotrocha, is obliterated, since, 

 as we see in fig. OO, the innei- end of the canal (the right in the 

 figure) lies wholly outside of the septum {jne.^.), that is to say, in 

 the trunk walls, as is known to be the case in the adult. Thus 

 we may assume that the formation of the infraseptal nephridial 

 funnels of the adult is due to secondary ontgrowths of the infras- 

 eptal portion of the atrophied, larval nephridial canals. 



Ectobladic Organs. As Caldwell has correctly o])served, the 

 larval tentacles and the greater part of the preoral lobe are torn 

 off and are digested in the stomach. I have very often met with 

 the remains of these organs in the interior of the latter [R, fig. 

 04«). Although I have said, in agreement with Caldwell, that 

 the greater part of the preoral lobe is cast olf, yet I can not 

 agree with the view entertained Ity several authors, that the epi- 

 stome of the adult developes from the remnant of the preoral lobe 

 of the larva. Because, according to my studies, the nei've ganglion 

 of the larva, whieh nearly marks tlie posterior limit of the lol)e, 

 can not at all be discerned in the larva at such a stage as is 



