SPERMATOGENESIS OF THE EARWIG. II3 



the young spermatozoa. The older spermatozoa arrange them- 

 selves in bundles by inserting their heads into a cyst cell. 



The material which is to form the spindle fibers is conspicuous 

 at an early stage and is very considerable in amount. It forms 

 another layer of fibers around the spindle proper (Figs. 5,21, 22). 



Something like the " mitosoma " described for Forficula by 

 Zweiger, 'o^, is present in Anisolabis (Fig. i), although the 

 form is apparently unlike in the two species. It is traceable 

 possibly from the spermatogonium to the spermatid ; but as it 

 does not stain with thionin after an early stage, and as it is very 

 small and there are many granules in the iron-haematoxylin 

 preparation, it is not by any means certain that the structures 

 observed are one and the same throughout the series (Fig. 20). 



The somatic chromosome number, found in the cells of the 

 ^Z% follicle, is twenty-four (Fig. 30). The material was not favor- 

 able for the examination of the ova. Very few were found in 

 division stages and only one was cut so that its chromosomes 

 could be counted. In this only equatorial plate observed the 

 number of the chromosomes is twenty-four. 



The characteristic structure of the male germ cells of Aniso- 

 labis Diaritinia is an equal heterochromosome pair which are pres- 

 ent possibly in the spermatogonia although they are not distin- 

 guishable from the other chromosomes in the spermatogonia! 

 divisions. In any case, it is formed anew in the telophase of the 

 last spermatogonia! division. It remains condensed during the 

 growth stages of the first spermatocyte and divides equally in 

 the first spermatocyte division, lagging behind the other chromo- 

 somes in the anaphase. It is not evident in the second sper- 

 matocyte division but there is a condensed chromatin body in 

 the spermatids. This equal heterochromosome pair appears to be 

 like the equal pair of idiochro'mosomes found by Wilson, '05, in 

 Nezara and the equal heterochromosome pair of Stevens, '06, in 

 Lepidoptera. 



Bryn Mawr College, 

 June 2, 1908. 



