200 Papers from the Marine Biological Laboratory at Tortiigas. 



The second division follows immediately and is even more abnormal 

 than the first. The centrioles scatter to the periphery and from each 

 there pass out radiations. With the dissolution of the nuclear membrane 

 or membranes, as the case may be, four new chromosomes make their 

 appearance; these all show a longitudinal split. Very soon, radiations 

 from a centriole are attached to each of the new chromosomes and they 

 are drawn to various points near the periphery of the cell. By this time 

 the ten vesiculated chromosomes remaining from the first division have 

 been inclosed in a sort of capsule and are thus prevented from participating 

 in the ensuing division. This is introduced by a slight elongation of the 

 cell. Next, the centrioles move to the two ends of the cell and in so doing 

 they form a spindk; one daughter chromosome then passes to each pole, 

 while the other chromosomes remain scattered in the cytoplasm. With the 

 division of the cell-body, the vesiculated chromosomes (inclosed in their 

 capsule) pass into one or the other of the daughter cells, where they are 

 set free by the dissolution of the capsule. 



As a result of this division, Meves holds that the new nucleus is formed 

 out of only a single chromosome, which very quickly becomes vesiculated 

 and increases in size; all of the other chromosomes are gradually dissolved 

 in the cytoplasm. Before the process of division is completed, cilia grow 

 out from the centrioles, forming a brush at each pole of the dividing cell. 

 After the cell has divided, the centrioles divide and their distal halves begin 

 to move across the cell. A connection in the form of a fiber is always 

 maintained between the proximal and the distal halves of the centrioles, 

 the former remaining attached to the cell-wall. The nucleus in the mean- 

 while decreases in size and its chromatin forms a layer under the nuclear 

 membrane. It moves closer to the plate of dividing centrioles. The con- 

 tinued movement of the distal centrioles across the cell results in pushing 

 the nucleus against the cell-wall and in forming the bundle of axial fibers 

 between the proximal and distal centrioles. Further growth of the axial 

 fibers is accompanied by a gradual lengthening of the cell until the typical 

 worm-shaped condition is reached. At the very end of the spermatozoon 

 the nucleus forms a thimble-like cap over the end of the bundle of axial 

 fibers. 



In formulating an hypothesis to explain the problematical function of 

 the oligop^'^rene spermatozoa, Meves discusses the theories of v. Brunn and 

 Brock. V. Brunn believed them to be rudimentary eggs and therefore 

 functionless, and this for two reasons: first, after careful investigation he 

 failed to find them either fertilizing the ovum or even present in the oviduct; 

 second, he believed their development bore resemblances to that of the ova. 

 These views Brock attempted to refute on the grounds that any such rudi- 

 mentary structure must have a proved homology with some still functioning 

 part or organ and its departure in structure and development must be 

 shown to be due to retrogressions; furthermore, if the dimorphism of 

 spermatozoa is to point to an ancestral hermaphroditism, as v. Brunn 



