228 NEIL S. DUNGAY. 



practically completed and many eggs were dividing the second 

 time. At 3:25 the majority of the eggs were in a 4 cell stage. 

 At 9:00 A.M. of the following day all were normal trochophores. 

 The second day brought forth setae and succeeding days showed 

 only a normal development. 34.1 consisted of fresh eggs and a 

 large quantity of sperm which had been kept in a corked vial 

 for 21 hours at room temperature. The sperm and eggs were 

 mixed at 1:35 P.M. Less than 5 per cent, of the eggs formed 

 jelly. At 2:59 P.M. there were many attempts to form a two 

 cell stage. It will be noticed that this is over 20 minutes longer 

 after insemination than the time at which the controls were 

 nearly through with the first cleavage. Very few normal 2 cell 

 stages resulted. Usually the constriction appeared in the proper 

 location but a few cases were observed in which the attempted 

 plane of cleavage would have divided the cell into equal parts, 

 had it been completed. In the great majority of cases the con- 

 striction lasted for a few minutes and then began slowly to dis- 

 appear, the cell becoming irregular in outline. For example one 

 cell was observed to be in the early process of first cleavage at 

 3:18 P.M. Slight progress was made for a minute and then no 

 change took place until 3:23 P.M. when the furrow began to 

 disappear. At 3:37 P.M. the furrow was invisible and there 

 was no trace of the attempted cleavage. Irregularities in cleav- 

 age were also seen. At 3:55 P.M. a 5-cell stage was noted. A 

 4-cell stage with two very large cells diametrically opposite to 

 each other was observed at the same time. Another distinct 

 5-cell stage was seen. Another 4-cell stage, as seen from a 

 polar view, had cells of equal size, the polar bodies appearing to 

 be normal. At 3:40 P.M. and following, another case of at- 

 tempted cleavage, similar to the one described above, was seen. 

 At 3:44 P.M. a 3-cell stage was found. Many one cell stages 

 which had formed jelly and thrown off polar bodies were now 

 evident. It was not determined whether many of these had 

 previously attempted to divide or not. Probably most of them 

 had not. At 3:45 P.M. a y-cell stage was seen. At 9:00 A.M. 

 of the following day most of the eggs with jelly were still in a 

 one cell stage or in irregular early cleavage. Much of this 

 irregular early cleavage is probably not a true cleavage but a 



