32O ROBERT H. BOWEN. 



always the same in any given lobe, all the spermatocytes in a lobe 

 being equally affected. There are accordingly three distinct 

 sizes of spermatocytes which give rise to three proportionally 

 different spermatids and these in turn to three kinds of sperms 

 with clearly marked morphological differences. But in the whole 

 series the amount of chromatin seemed to be identical, the chro- 

 mosome sets of the maturation divisions being similar in every 

 respect. Montgomery examined a number of related genera but 

 found no such size differences, or at least no conspicuous ones. 



My attention was first attracted to this problem by the dis- 

 covery that Murgantia Jiistrionica also exhibits size-differences 

 similar to those of Euschistus but much less conspicuous, two 

 lobes having large and three lobes normal-sized spermatocytes. 

 The expected two kinds of spermatids and sperms (Figs. 34 and 

 35) were also found. These facts aroused the suspicion that 

 " dimegalous sperm " were by no means unique to Euschistus as 

 Montgomery had supposed, and accordingly it occurred to me to 

 make a survey of the whole Family Pentatomidce with respect to 

 this particular point. The results fully confirmed my suspicion, 

 for of thirty-seven species examined, twenty showed visible size 

 differences, sometimes of three classes, sometimes of two. Fur- 

 thermore, every degree of relative difference was found, ranging 

 from the inconspicuous difference in Murgantia up to a most re- 

 markable difference in Arvelius, where the whole testis is domi- 

 nated by the large generations of spermatocytes. I found, 

 further, that every part of the cell shares in this differential 

 growth except the chromosomes the nucleus, cytoplasm, plas- 

 mosome, mitochondria, Golgi apparatus, acrosome, centrioles, 

 spindle and chromatoid body being of a size roughly proportionate 

 to that of the cell as a whole. It might be supposed that the 

 morphology of the cytoplasmic constituents would be affected by 

 these size differences, and indeed some differences do occur, but 

 they appear to be of quite secondary importance. Finally, I have 

 found that the processes by which the sperm head is differen- 

 tiated differ rather strikingly in the large and small cell genera- 

 tions, as will be indicated. 



Concerning the significance of these facts, we are at present 

 quite in the dark, nor do we know that the " polymegalous " 



