STUDY OF CHROMOSOMES OF LACHNOSTERNA. 93 



the spermatogonia are arranged in the form of a rosette, and are 

 now triangular or wedge-shaped with the nucleus at the base and 

 the rest of the cytoplasm extending toward the cyst cavity. 

 Thus, with the formation of the cyst, there is a polarity estab- 

 lished in the spermatogonia which is maintained up to the for- 

 mation of the ripe spermatozoa, for, the side where the nucleus 

 is located is destined to form the head of the spermatozoon, and 

 the cytoplasmic portion extending toward the cyst cavity is 

 destined to form its tail. Hegner. ('14) has homologized the 

 process of cyst formation with the differential divisions in insect 

 oogenesis which establish nurse cells and oocytes. It has long- 

 been known that the insect egg possesses a remarkable polarity 

 besides being highly organized. Since, as it has been above 

 shown, the polarity of the sperm cells are established at the time 

 of cyst formation, and since this process is homologous to nurse 

 cell-oocyte differentiation, it is probable that the polarity of the 

 egg may have its origin at the time of the differentiation of 

 nurse cells and oocytes. 



3. Linin and Chromosome Structure. 



When one studies the history of the chromatin of the nucleus 

 from the resting stage through the synaptic period up to the 

 reconstitution of the definitive maturation chromosomes, one 

 begins to seek for some of the underlying mechanisms concerned 

 in the movements of the chromatin particles. From the diffuse 

 granular state of the chromatin up until the formation of the 

 chromosomes, the linin network of the nucleus plays an active 

 part. Chromatin granules in the nucleus are never isolated 

 as such, but always have linin connections with other granules. 

 The synaptic threads consist of linin threads with the chro- 

 momeres embedded along them. As has been before stated, 

 homologous chromomeres have linin connections running between 

 them. Conklin ('17) has shown that the ground-work of the 

 cytoplasm is the relatively stable and elastic spongioplasm, and 

 he attributes to it the maintenance of cytoplasmic organization 

 and the movements and localization of cytoplasmic substances. 

 Similarly in the nucleus it seems that the linin is a relatively 

 elastic substance which forms the ground-work of the nucleus 



