GERM CELLS OF COELENTERATES 43 



details as the form of spindle, distinctness of chromosomes, and 

 the like, but the principles involved are those characteristic of 

 similar phases in germ cells generally. In some instances con- 

 ditions are found which have been interpreted as synizesis, in 

 other cases such phases were not found. The coelenterates do 

 not, therefore, add anything definite to the evidence concerning 

 the normality of this process. 



While the chromosomes appear to show a characteristic be- 

 havior, they are lacking in the variety of form and size which 

 obtains in the chromosomes of some animals. In most coelen- 

 terates whose chromosomes have been studied, there is a simi- 

 larity which renders it very difficult even to identify synaptic 

 mates in maturation mitoses. Of the forms studied by the 

 author only Aglantha had chromosomes which offered a reason- 

 able opportunity for a study of details. Oogonial chromosomes 

 did not, however, readily lend themselves to a grouping into 

 homologous pairs. Some doubt was expressed as to whether 

 these chromosomes behaved in quite the fashion believed to be 

 characteristic and tj^jical of maturation mitoses. The evidence 

 is not sufficient to warrant any definite conclusions of a differ- 

 ence in the chromosome behavior of the coelenterates. 



The question of the individuality and continuity of the 

 chromosomes has been in mind during the study of the coelen- 

 terate germ cells. On one point the evidence is clear. During 

 interkinesis there is no indication of the persistence of the 

 chromosomes, the 'resting nucleus' is typically a single vesicle 

 clearly without division into smaller vesicles. In certain forms 

 chromosomal vesicles are produced after maturation or cleavage 

 mitoses, but it is very common for two or more chromosomes to 

 form a single vesicle. In any event, if the period of inter- 

 kinesis is long, these vesicles unite into a single one. On the 

 matter of the maintenance of chromosome individuality during 

 interkinesis Wilson ('13) says: 



Some of the most careful recent cytological studies in this direction 

 seem to show that such is not the case. Nevertheless these same 

 studies, together with recent experimental evidence, give very strong 

 ground for the conclusion that a definite relation of genetic continuity 

 exists between the individual chromosomes of successive generations 

 of cells. 



