No. I .] SPERM A TOGENESIS OF BA TRA CHOSEPS. 1 9 



are comparatively rare. In most instances they can only be 

 counted here and there in the same chromosome, the trouble 

 generally being that the chromosome has not been properly 

 differentiated. But wherever glimpses of the chromioles are 

 had it will be seen that they are arranged in rows, one row on 

 either side of the chromomere, and parallel to the longer axis 

 of the chromosome. As is to be expected in a case like this, 

 where we view an object of so small a magnitude that it lies 

 on the limit of vision, it is a most difficult matter to count the 

 chromioles and to be sure that the count is correct. I have 

 made a number of countings, almost wherever I found a suit- 

 able opportunity, and the result is that I consider the number 

 of chromioles constant in every chromosome of regular size. 

 Thus in the metaphase-chromosome of the auxocytes and sper- 

 matocytes there are three chromomeres in each prong, or six 

 chromomeres in all, making six chromomeres for the whole 

 chromosome. Each chromomere contains six chromioles, 

 three at each margin, which makes thirty-six chromioles for 

 the whole chromosome. The regularity of the chromioles, 

 both as regards number, size, form, and arrangement, precludes 

 the possibility of their being artefacts, and we have no alterna- 

 tive but to assume that they are bodies of permanent structure 

 and of the highest importance. The question now arises, to 

 what extent can we trace the chromioles, backwards as well as 

 forwards, in the development and evolution of the chromosome. 

 This subject will be more particularly entered into when we 

 discuss the development and evolution of the nucleus, and 

 here it must suffice to give only a brief outline of the results 

 of my observations. The chromioles can be readily observed 

 in all the different stages through which the chromosomes pass, 

 except in the confluent umbrella stage in which I have so far 

 not been able to view them with any degree of satisfaction and 

 clearness. In that stage there exist in the confluent mass 

 besides the endochromatic bodies numerous dark staining gran- 

 ules, but they are irregularly scattered and stain darker than 

 the chromioles in other places. But while the persistence of 

 the chromioles in this stage has not been satisfactorily demon- 

 strated, it is at least highly probable, as immediately when the 



