510 I. IKEDA : 



took place in the bodv-cavities, and accordingly, as CoRi reinai'ks, 

 lie nuist have believed that ;r;elt-lertilization prevails in Phoro- 

 nw. Cori considers this as hi^hl}^ improbable, bnt does not 1)rini;- 

 forward any positive facts in contradiction of it, his inference 

 being di'awn solely from facts ol)servcd in other marine jMetazoa. 



Since Kowalewskv's valuable researches ('67), it has 

 generally been accepted that the ne[)bridia serve also as oviducts. 

 Thus Uenham says that he saw an ovum iittached to one side 

 of the ne])hridial funnel and further mentions that Kowalewsky 

 observed eggs moving through the nephridial canal towards the 

 exterior. Unfortunately both ol)servers failetl to elucidate what stage 

 of develo})ment these eggs are in. 



In PJioronis ijimal mature sexual elements are constantly 

 discovered tbroughout aljout oue half of the year (frimi November 

 to May or June). ]]y carehdiy examiniug a living colony ofthat 

 species during this])eriod, it will s(X)n be j)erceived that some indivi- 

 duals ditter slightly from the rest in the aspect of the fool or 

 body. We see in them a moniliform series of small white specks 

 shining through the skin in the uppermost part of the bod_y. 

 These are the ova ready to escape to the exterior through the 

 nephridia. It nuist have been such individuals that were observed 

 by Kowalewsky and Bexham. The Injdy-cavit^^, in which the 

 ova lie, corresponds to the rectal chamber near the anterior end 

 of the body. I have endeavoured to ascertain whether these ova 

 are fertilized or not, and have at last succeeded in ascertaining 

 that they are in a stage prior to the extrusion of polai- globules, 

 — the primary oocytes, in Bon'ERl's terminology. In the fresh 

 state, they are spherical or somewhat elliptical in shape and ])er- 

 fectly opaque by virtue of the abundant yolk-granules contained in 

 the vitellus. It is characteristic of these ova that the nucleus, which 



