Nos. 455-456.] 



FASCIOLARIA. 



879 



shown. Large nuclei of irregular shape (Fig. 12) are also found 

 in the endoderm of this stage ; thev are a]))>arentlv also forms 

 of amitotic division. Their exact ri'lation to tin- niorc t\i)ical 

 cases could not be (leterniiiK'fl 

 from the material which 1 IkuI. 

 They are quite commonly lo be 



embi 



little 



oldci stage but bcloK- the endo- 



form. Nuclei of both these forms 

 predominate decidedly during the 

 development of the embryo, but 

 in addition to them there are 

 occasional nuclei showing un- 

 mistakable karyokmetic figures. 

 The latter are too inlrequent to 

 be regarded as the nuclei from 

 which the rapidl)- growing en- 

 doderm is being chieHy regener- 

 ated, but there is nothing to show 

 that they do not give rise to en- 1 ,, --.nf.c. view (tangen 

 doderm cells as well as the ami- ' s! ak''= rlrmnf 



totic nuclei. The presence ol 



the mitotic figure is a guarantee ot the a(le(|uac \ ol 

 nique, whatever we may think of the amitosis 111 these 

 least it is not possible to dispose ot them as artihu 

 recall in this connection the cases ot amitosis m the 

 cells of isopods observed by Ryder and Miss I'ennii 

 referred to bv Conklm These were shown bv 1 



rtifac 



. du( 



the endoderm, for at the time the\ lue swallowed the layer has 

 not as yet been formed ; they grow out into the cavity after the 

 ova have been swallowed. Atter a stu(l\ ot the a\ailable mate- 

 rial I have not been able t.. resist the conviction that m Fascio- 

 laria we find a true case ot embrs oiiic- cells multiplying, contrary 



