434 J. A. MURRAY, 



same; it is at any rate much greater than twelve. The divisions of 

 the spermatogonia are characterised by a much larger number and in 

 those cases where it has been possible to count, as nearly as could 

 be made out, forty-eight. This is interesting as Vom Rath^) gives 

 the somatic number of chromosomes for Helix as twenty-four — the 

 reduced number as twelve. Platner counts in the first ripening 

 division twenty-four, in the second twelve. I have never seen pre- 

 parations with twelve rings in the first ripening division although I 

 have examined material collected from widely separated parts of 

 Germany, and in the absence of such, decline to decide whether there 

 are here two varieties comparable to Äse. meg, univalens and bivalens, 

 or whether a diff"erence in interpretation of the microscopic images is 

 the explanation. 



Y. Conclusion. 



The observations recorded above, are so little in favour of the 

 nuclear nature of the Nebenkern, that it would be preferable to drop 

 the term altogether. At present any doubtful structure in the proto- 

 plasm of cells belonging to the cycle of spermatogenesis, is dubbed 

 Nebenkern and each author is under the necessity of defining his use 

 of the hackneyed term. Some purely descriptive name, such as 

 archoplasm mass or attractionsphere (although this is also open to 

 objection), should be adopted till our knowledge of these structures 

 is more advanced. 



Whether the sphere fragments are partly transformed into the 

 radiations is very difficult to decide. It is certainly very suggestive 

 of such a fate, that, in preparations which show the Nebenkern in 

 resting cells, and even in late prophases, with diagrammatic clearness, 

 the fragments in amphiaster and metaphase are smaller and much less 

 strongly stained, or even completely decolourised. 



The cause of the disintegration of the attractionsphere as mitosis 

 begins is not very clear. Probably, the entrance of new material into 

 it in connection with the increased activity of the centrosomes, dis- 

 tends it and ultimately separates the lobules from each other. It is 

 difficult otherwise to comprehend the sudden increase in the number 

 of radial fibres and the recession of the fragments from the centro- 

 some. 



1) Vom Rath, 0., Zur Kenntniss der Spermatogenese von Gryllo- 

 talpa vulgaris, in: Arch. mikr. Anat., V. 40, 1892. 



