134 FERNANDUS PAYNE. 



This number and the size relations are exactly what is found 

 in the female cells (Fig. 5, A and 5). Again, if the 12-chromo- 

 some class meets the same egg we would expect 26 chromosomes 

 in the offspring, three of which should be small, and this number 

 and relation is confirmed by the figures of the male cells (Fig. 

 5, C, D, E and F). From the facts at hand, it is evident that the 

 reduced number of chromosomes in the egg is 14 and that three 

 of these are decidedly smaller than the rest. Females must 

 therefore be produced upon fertilization of the egg by the 14- 

 chromosome class of spermatozoa; males by the 12-chromosome 

 class. 



Egg 14 plus spermatozoon 12 = 26 ($), 

 Egg 14 plus spermatozoon 14=^=28 (?). 



From the above observations, it becomes apparent that the 

 three small chromosomes and one other, which is not recognizable 

 in the spermatogonial divisions, do not pair at synapsis. This 

 gives an explanation of Montgomery's unequal pair. 



Prionidus thus gives us a second new type of chromosome dis- 

 tribution and presents the intermediate stage between the types 

 illustrated by Fitchia and Gelastocoris. 



Montgomery has described only the rest stage of the growth 

 period. In his earlier paper COT) he says: "In the rest stage 

 of the spermatocyte are found four chromatin nucleoli attached 

 to the true nucleolus. One of these is longer than the others 

 and rod-shaped." Later ('06) he describes this stage somewhat 

 differently. ' In the complete rest stage of the spermatocytes are 

 found three or four safrininophilous bodies attached to the sur- 

 face of a large more or less central plasmosome. They are of 

 unequal volumes ; and when there are three of them, each appears 

 bipartite, while when there are four, the smallest are each uni- 

 partite. Perhaps as in Sinea, these relations are to be inter- 

 preted as three bivalent diplosomes, the smallest of which may 

 sometimes have its parts separated." 



I have followed the history of the differential chromosomes 

 during the growth period somewhat in detail as the material 

 proved favorable for this purpose. Between the last sperma- 

 togonial division and synapsis, a pale plasmosome persists. At 



