128 N. YUTSU. 



there is no gut at all, these being not far from the " Dauerblas- 

 tulae " (26"); in other cases the gut is represented by a shallow 

 depression (2 A"). In some defective larvae either the stomach or 

 the oesophagus may be wanting (28, 2/T). In a few cases the 

 stomach is cut off from the oesophagus (2E). 



It is noteworthy that there occur a few defective larvae which 

 are as large as the perfect ones (2A). And among the perfect 

 pilidia only three were smaller than the others. 



From the increased number of defective larvae in this series, it 

 may be inferred that, since the fading of the germinal vesicle, the 

 regional specification has advanced. But the occurrence of per- 

 fect pilidia equal in number to the defective ones cannot be over- 

 looked. It is possible that the production of the perfect larvse 

 is because the injury was too small to have materially affected 

 the organ-bases, or because the plane of section was such as not 

 to disturb their normal proportions. The number obtained is, 

 however, too great to lend much probability to either of these 

 suggestions. A more likely interpretation is that the egg still 

 possesses a considerable power of regulation. 



SERIES C. 



Development of Fragments obtained at t/ie Period of Conjugation 



of the Egg- and Sperm-nuclei. 



The eggs were fertilized and a portion of cytoplasm was cut off 

 a little after the second polar body was extruded, /. e., at about 

 the stage at which the egg and sperm nuclei 

 came to fuse. In this series the polar bodies 

 gave a very good landmark for orientation of the 

 egg. The accompanying cut shows the direc- 

 tion of section plane (Fig. 3). The eggs which 

 were able to develop up to pilidium were not as 

 FlG numerous as in Series B, but they gave a fairly con- 



clusive result, as shown in the table on p. 102. 

 Most of the pilidia of this series are defective, as tabulated. 

 Not only that, the defective parts correspond in a general way 

 to the region from which the cytoplasm was cut. 1 It is very 



1 The apparent contradictory result as in the case of Nos. 17 and 23 is probably 

 due to the volume of the cytoplasm cut oft". 



