[)Q S. GOTO. 



tlieii niiis forwards on the left side of the oVnr}', tlien towards tlie rii^-lit, 

 then ag'ain forwards, nnderg'oinir more or less winding's on the wa}^, 

 and then towards the dorsal side of the ])enis, which it erjters near its 

 h'lse and, traversini>' it lonu'itndinally, finally opens into its caA'ity 

 near or at its apex, jnst as in Trisfoiiiiini (IM. XXVI, tiu's, 1, o, 4, 

 & ()). Dni'inii' its course the vas deferens nndero-oes nnnierons con- 

 sti'ictions and enlargements. 



In Microcoiijlc, A.xim\ Diclidophora, ( kUocotiile, llcxacoiijJc, Calicn- 

 tijle, i\[onocotiih\ and OtirliocnttjJe I liave not been ahle to (observe the 

 vasa etferentia. In these u'cnera, the irre^'ulai' r-avities of the mes- 

 enchyni:i l)etween tlie testes probahly ser\e as such. The singde vas 

 deferens, howewr, can in all these genera he followed witli certainty 

 up to the testes. In Cdlicoh/Ie the vas deferens proceeds forwards on 

 the left side of the median portion of the body to near the pli:u*ynx, and 

 then turns backwards and towards the riHit and contirmes its course 

 into the penis. In most of the other geneni above mentioned, the vas 

 deferens takes its origin from the testes more on one side of the l)ody, 

 right or left according as the case may be, and undergoing numerous 

 windings on its course forward, opens finally int(i the genital atrium. 

 When the uterus and the vas deferens come to lie in the same sagittal 

 plane, the latter is always situated on the dorsal side, and opens into 

 the genital atrium also more dorsally than the former. In A.rinc 

 and Microcoti/h' the vas deferens proceeds foi- wards on the ventral 

 side of the ovary (Pis. I, II, & ^^T). 



The wall (^f the vas deferens consists in most species of a 

 structureless, refractive membrane <^f varyino- thickness accordino- to 

 the species, and whfjlly destitute of nuclei ; Ijut in some species there 

 is a niore or less distinct protoi)lasmic layer separated from the 

 mesenchyma Ijy a basement membrane, and exhibiting at irregular 

 distances, rounded or oval, well-stained luiclei, usually containing 



