SPERMATOGENESIS OF AMERICAN CRAYFISH 621 



The possibility suggests itself that the trimorphism of the sperm 

 in Cambarus virilis may perhaps be accounted for by the behavior 

 of the chromatoid bodies. This must remain a possibility only, 

 since the chromatoid bodies cannot be followed through the 

 transformations undergone by the resting spermatids to form the 

 spermatozoa. However, it is a striking fact, that three types of 

 spermatids, types A', B' and C are produced in this species, and 

 also, that type C is about four or five times as numerous as either 

 of the other two. Since the coincidence of almost an exact 

 trimorphism is noticed in the mature spermatozoa, it seems to 

 point to the possibility that the chromatoid bodies are responsible 

 for this interesting difference. In Cambarus immunis the chro- 

 matoid bodies were not found. This was probably due, however, 

 to the fixation of the material. 



GENERAL CONSIDERATIONS AND CONCLUSIONS 

 L Synapsis and reduction of the chromosomes 



The problems of synapsis and chromosomal reduction are 

 perhaps the most important in the study of the germ cells. Con- 

 siderable has been written on these questions, but recently, 

 Gregoire ('10), Montgomery ('11), and Wilson ('12) have given 

 us critical discussions of them. Montgomery ('11, pp. 749-750), 

 has ably summarized the various views in the following way: 



I. The actual reduction of the number of chromosomes is effected 

 during the prophase of the maturation mitoses, and both of these 

 divisions are equational. This [view] was originated by Boveri ('87) 

 and Brauer ('93). Today it is held in two forms: (A) Meves ('96, '07a) , 

 Fick ('07, '08), and Duesberg ('08) argue that a continuous spirem is 

 pfoduced, that this segments into half the normal number of chromo- 

 somes, the cleft along such a bivalent chromosome being a true longi- 

 tudinal split ; they reason there is neither metasyndetic or parasyndetic 

 conjugation of chromosomes. (B) Bomievie ('06, '08) and Vejdowsky 

 ('07) hold there is a parasjTidetic union of chromosomes, but that this 

 conjugation leads to complete and persisting fusion. 



II. The reduction of the number of the chromosomes is effected by 

 the maturation mitosis, one at least of which is a reduction division. 

 There are several variants of this, as follows: 



A. The univalent chromosomes, without conjugation or pseudo- 

 reduction, double their number during the prophases, then become 



