272 ^- ^nTSTiKURi. 



wnlJ. This course of reasonînof reduces Will's views practically to the 

 same thing as mine as given in Cnntrib. IIT. with the exception of the 

 single ]ioint that I consider tlie *' Zwischenplatte " as a flattened 

 diverticulum, while he does not. I have already urged above the 

 reasons for my views, so that I will not again go into them. I 

 must refer the reader to it as well as to my C<^ntrib. III. Notwith- 

 standing that A¥ill says, I have fallen into a fundamental error in con- 

 founding " Septenbildung " and " Divertikelbildung," I still think, 

 I was not without reason, when I snid in my note (Anat. An:. No, 

 12 and 13, 1893. p. 4o4). that ■' * ->^ ::- whether the ])resence of the 

 fold is emphasized or the diverticulum is pointed ont as the essential 

 feature does not alter the facts of the case much. Will's objection to 

 Hertwig's theory may therefore be only an apparent one." The 

 difference between " Septenbildung " and " Divertikelbildung " which 

 Will points out is exactly like that lietween the process of budding and 

 of division. It is not possible to draw a hard and fast line in one 

 case as in the other. 



Finally I would like to add that while Will and myself agree as to 

 the essential features of the reptilian development, the above discussion 

 shows that on nifiny minor points we must for the jn-esent " agree to 

 disagree," (as I lieard the late Prof. Balfour i-emark on a similar occa- 

 sion), until fresh observations bring out new facts and enable us to 

 settle these vexing points. 



I have very recently received througli the kindness of the 

 author, Keibel's " Studien zur Entwicklungsgeschichte des Schweines." 

 (Morphologische Arbeiten. III). It would perhaps be going out of 

 my way too far to offer any extensive remarks on this article in- 

 teresting though it is to me. The foregoing paper shows that, like 

 himself, I divide the gastrulation into two phases, but these two 



