12S 



decidedly ruby red tinge, not noticeable in my sections in any other type 

 of cell in the whole worm. 



These yellow cells are found in the testicles during the younger stages 

 of development; they disappear before maturity and apparently are con- 

 cerned with the nutrition of the blue cells which finally produce the 

 spermatozoa. 



The " blue " cells difier very much in size during the various stages 

 they pass through ; their cytoplasm is, when present, always blue (except 

 detritus remaining after formation of spermatozoa, which eventually turns 

 vellow). Their nucleolus never reaches the size of that of the " acid " 

 cells. 



For some time, and until the testes have reached a fair state of 

 development, the multiplication of both types of cells appears to take 

 place bv amitotic division of the cells into two, the resultant cells not 

 arranging themiselves radially (spermatogonia). 



After these preliminary divisions, one finds both blue and yellow 

 cells undergoing division, by which the resultant new cells (sperma genes) 

 lie arranged radially (Fig. 7), connected in the centre by thin filaments 

 of protoplasm, yellow in the case of " acid " cells, blue in the case of the 

 normal spermagene. 



This stage resembles the " first phase of proliferation " Bugnion and 

 Popoff saw in the spermatogenesis of Lombricius agricola (Bugnion and 

 Popoff, La Spermatogenese du Lombric, Zool. Congress, Berne, 1904). It 

 is followed as in the earth-worm by a phase of dissociation, especially 

 marked in the case of the acid cells which separate entirely. The blue 

 cells (spermatocytes 1), on the other hand, remain connected to the centre 

 of radiation by their protoplasmic processes for some time, increasing in 

 size ; their nuclei becoming denser and darker as the cells increase in 

 size, but without changing in magnitude (nuclei soon after proliferation 

 4i- /^, after increase of cell 4^ ,«). After proliferation chromatin in small 

 peripheral globules, after growth of cell in larger masses filling the nucleus. 



The basal cells do not seem to divide again, but degenerate and finally 

 disappear. 



Just before the second proliferation of the spermatocytes the chromatin 

 again changes, first forming small globules, then stretching itself out into 

 threads. The next change appears to be that the cells forming one of the 

 radial figures left after the first proliferation and dissociation fuse, the 

 nuclei resolve themselves into chromatin threads and wander into the 

 interior of the syncytium, all traces of the single component cells becoming 

 lost. The nucleoli remain visible until the chromatin has drawn itself 

 out into threads ; it then also appears to form threads. The chromatin 

 then seems to break up into short lengths, each of which at the surface 

 forms the nucleus of a new cell (spermatid). These cells after further 

 division give rise to spermatozoa. A large quantity of cytoplasma and 



