No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 21 



their final number, then we find that each chromomere con- 

 tains six chromioles, just as before (Figs. 24, 48, etc.). As the 

 chromomeres fuse into each other, the chromioles also become 

 correspondingly more closely set and finally they appear in the 

 chromosome as two parallel strings imbedded in a common 

 sheath of chromoplasm. This leads us up to the very point 

 from which we started, the perfectly formed chromosome in 

 the metaphase. We can, if we wish, follow this process all 

 through the evolution of the polymorphous spermatogonia, the 

 auxocytes, the spermatocytes, and partly also into the sperma- 

 tids, though the latter are so minute that their finer structure 

 can be less satisfactorily studied. In order to test the existence 

 of chromioles in chromosomes of other animals, I have fixed 

 testes, by the iridium-chloride method, of a number of other 

 animals, especially of insects, and I am thus able to state that 

 in every instance where the chromosomes are of sufficient size 

 to allow of a closer study, I have been able to demonstrate 

 satisfactorily the existence of the chromioles. They are espe- 

 cially well defined in species of orthoptera (Stenopelmatus). 

 From the above observations I conclude that the chromioles 

 are permanent structures in the chromosomes, and that they 

 are the smallest visible individualized and organized parts of 

 the chromosomes, and further that the chromoplasm, the chro- 

 momeres, and the chromosomes are merely structures for the 

 conveyance of, the nourishing of, and the partition of, the 

 chromioles. 



There yet remains to say a few words about the division of 

 the chromioles. The proper increase of the chromioles is, of 

 course, an absolute necessity, provided we are correct in assum- 

 ing them to be the most important parts of the nucleus. As 

 the chromioles are too small to allow of any direct observation 

 as regards multiplication, all speculations on this subject are as 

 yet premature. The counting of the chromioles is a most diffi- 

 cult matter, as not even under the most favorable circumstances 

 can all the chromioles in the same chromosome be counted. 

 The best we can do is to approximate and average their num- 

 ber. I have stated that in the early anaphase we find at each 

 pole twelve chromosomes, each one containing about six more 



