SPERMATOGENESIS OF AMERICAN CRAYFISH 



623 



Vertebrates: Man, rabbit, cat, mouse, rat, pigeon, garden 

 snake, Triton, salamander, Chimaera, Raja, Spinax, Bdellostoma, 

 myxine. Arthropoda: Locusta viridissima, Eucheata norvegica. 

 Annelids: Tomopteris onisciformis, Ophryotrocha puerilis. AIol- 

 luscs: Enteroxenas ostergreni. 



In Tomopteris these authors obtained especially fine material 

 and have traced out the parallel conjugation of the chromosomes 

 in the most convincing way. Table 2 gives a list of the investi- 

 gators who have found such conjugation in animals, with dates 

 and the forms in which it occurs. 



In the species of Cambarus studied the problem of synapsis 

 is one of especial difficulty due to the immense number of chro- 

 mosomes possessed by the forms. When the leptotene threads 

 appear, these are so numerous that it is impossible to count them. 

 However, in synizesis these are seen to drift to one pole of the 

 spindle and to become arranged in pairs, the individual threads 



TABLE 2 



AUTHORS AND DATES 



(1) Mammals . 



(2) Birds 



(3) Reptilia.. 



(4) Amphibia. 



(5) Fishes. 



(6) Insects. 



(7) Crustaceans. 



Von Winniwarter ('00, '02) 



Schoenfeld ('01) 



A. and K. E. Schreiner ('04) 



A. and K. E. Schreiner ('04) 



A. and K. E. Schreiner ('04) 



Janssens ('05) 



A. and K. E. Schreiner ('06) 



Marechal ('04) 



A. and K. E. Schreiner ('04, '05 and 



'06) 

 Otte ('06) 

 Morse ('09) 

 Montgomery ('11) 

 Wilson ('12) 

 Wilke ('13) 

 Kornhauser ('14) 

 Lerat ('05) 



rsi Mnlhmcs ^ Bonnevie ('05, '06) 



(8) Molluscs I \ A. and K. E. Schreiner (-07) 



(9) Annelids ; A. and K. E. Schreiner ('06a, '06c) 



,.^. TVT * 1 / Tretjakoff ('04) 



(10) Nematodes <^ ■" ,; 



I ( Marcus (06) 



