278 



A n D u 1 a t a. 

 Arenicola cristata. Each ovary in this species is situated 

 on the wall of a blood vessel which extends along the nephridiuui. 

 The animals produce an enormous number of eggs throughout most 

 of the summer. Passage of the eggs to the exterior occurs more than 

 once — probably several times— during the season. Ovaries of this species 

 sectioned during early summer and when the coelom contained eggs 

 of all sizes from those just set free from the ovary to those fully 

 grown show very large numbers of primitive oogonia and every indi- 

 cation of rapid production of new cells. As yet, however, I have not 

 been able to find a single case of mitosis in these sections. My ob- 

 servations here are not very extensive and it may be that mitosis does 

 occur. Synapsis stages are frequently seen and may readily be mistaken 

 by the casual observer for early stages of mitosis, but numerous cases 

 of what appears very clearly to be amitosis are present in all sections 

 which include stages before synapsis. In Figure 4, I — V, a number of 



Fig. 4. 



cases all taken from a single sections'are shown. This same section 

 contained many more equally convincing cases. These phenomena are 

 exceptionally distinct and clear in this form and error seems impos- 

 sible. 



In connection with my other work along this line it occurred to 

 me recently that the so-called cessation of cleavage in various embryos 

 and larval forms might be at least in some cases a change from niitotic 

 to amitotic division. Unfortunately I have not been able as yet to 

 obtain any large series of preparations for testing this point. Having 



