MATURATION OF OVUM IN ECHINUS ESCULENTUS. 209 



apart of tlie U's or Vs at the apex in tlie anaphase is 

 held to be a transverse division of the original long 

 chromosomes. Griffin alone says that the possibility of a 

 second longitudinal cleavage is not absolutely excluded, 

 but as the T-shaped figure is rare, he held to the other 

 explanation. It is obvious that it is extremely unlikely 

 that such exactly similar appearances should arise in different 

 ways. I believe that the demonstration I have given of the 

 nature of the process as it is seen in Echinus might, if 

 applied to them, reconcile all these instances with what is 

 known to occur in Amphibia and the higher plants. A certain 

 part of the contradiction in results would thus be removed. 



2. 3. 4. 5. 6. 



Text-fir. 1. — Scheme showing the successive stages in the resolution 

 of the chromosomes in the " heterotypictil divisions " according to 

 an interpretation which makes the apical break of the V atrans- 

 verse cleavage. (After Wilson.) 



and instead of these cases being held to prove a reducing 

 division in Weisstnann's sense, they would, as does Echinus, 

 disprove it. 



The figures given by Linville (1899) for certain pulmonate 

 Gastropods are very similar to those described in this group, 

 but the origin of the figures is not completely worked out. 

 He decided for a longitudinal division in the first division, 

 and the elements are doubled in the anaphase, while these 

 again are distributed in the second division. 



On the other hand, in Helix pomatia, Bolles Lee (1897) 

 describes appearances which lead him to conclusions different 

 from most other observers. He finds transverse divisions in 



VOL. 46, PART 2. — NEW SKKIES. O 



