224 NEIL S. DUNGAY. 



results were found, indicating that maturation and jelly formation 

 had been initiated by the sperm in some way, although later 

 development failed to take place. In some experiments this 

 has been seen in more than half of the eggs which formed jelly. 

 All experiments which gave any indication of abnormality con- 

 tained at least a few of this type of eggs. In those, cultures in 

 which these eggs were present in considerable numbers I failed to 

 see as many fertilization cones as usual. This suggests either 

 that the eggs were infertile, due to the failure of the sperm to 

 enter, or that the development was carried this far in response to 

 some unknown stimulus given at the time of insemination. 

 Cytological examination is necessary to determine this point. 



(c) Cytological examination of stained sections showed cases 

 in which polar bodies appeared without jelly formation. No 

 indication of this was seen in the living material as it was not 

 supposed that it was possible. It would, of course, be difficult 

 to find, even if such cases were known to occur. 



(J) Development sometimes stopped after the first cleavage 

 or more rarely after the second. This occurred in less than 2 

 per cent, usually. It was usually associated with 



(e) an unsuccessful attempt to form a first cleavage plane. The 

 behavior of such cases will be described under another heading in 

 more detail. 



(/) In some cases, as many as 0.5 per cent, in one experiment, 

 the first cleavage plane divided the cell into two equal parts. 

 Such cases did not usually divide again. 



(g) In a very few egg cells the cleavage was uneven, forming 

 3, 5, or 7 cell stages which usually died without developing far. 

 It is well known that uninseminated eggs may undergo a kind 

 of pseudo-cleavage if allowed to stand for some hours but the 

 cases mentioned here are not to be confused with this for several 

 reasons. Their appearance is different. These forms appear 

 much earlier than they ever do in the unfertile eggs. The control 

 of unfertilized eggs never showed such pictures until much later 

 and then they were of a different appearance. 



(7z) Other irregular forms of cleavage were seen, but very 

 rarely. Since the later cleavage stages are more complex in 

 appearance it is more difficult to find irregularities and they 



