102 bulletin: museum of comparative zoology. 



strepsinema and is by no means regular" .... Further on (p. 753) he 

 says : — " During the past year I have also convinced myself of the 

 occurrence of parasyndesis in Plethodon, such as Janssens had de- 

 scribed for this object and the Schreiners for Salamandra." 



Wilson ('12), in his critical study of the subject, first states the 

 questions that he believes must be answered in connection with synap- 

 sis and then gives his reasons for believing in the wide occurrence of 

 parasynapsis. He regards the following questions as still awaiting a 

 satisfactory answer: — "1. Is synapsis a fact? Do the chromatic 

 elements actually conjugate or otherwise become associated two-by- 

 two? 2. Admitting the fact of synapsis, are the conjugating ele- 

 ments chromosomes, and are they individually identical with those 

 of the last diploid or premeiotic division? 3. Do they conjugate 

 side-by-side (parasynapsis, parasyndesis), or end-to-end (telosynapsis, 

 telosyndesis), or in both ways? 4. Does synapsis lead to a partial 

 or complete fusion of the conjugating elements to form 'zygosomes' 

 or 'mixochromosomes,' or are they subsequently disjoined by a 

 reduction division?" 



Wilson finds his own material (hemipteran) not altogether favorable 

 for a solution of the problems enumerated, but has been able to study 

 the preparations of Tomopteris, supplied by the Schreiners, and of 

 Batrachoseps supplied by Janssens. He studied also some orthop- 

 teran material, including Phrynotettix, secured from McClung. 

 After a study of Tomopteris and Batrachoseps he says (p. 384): 

 "Through the study of Batrachoseps and Tomopteris I have finally 

 been convinced — for the first time, I must confess, as far as the auto- 

 somes are concerned — (1) that synapsis, or the conjugation of 

 chromosomes two-by-two, is a fact, and (2) that in these animals 

 (perhaps also in the Orthoptera) the conjugation is a side-by-side 

 union, or parasynapsis." And again (p. 399), "The few observations 

 I have been able to make on McClung's preparations of Achurum, 

 Phrynotettix, and Mermiria. . . .lead me to the impression that a 

 side-by-side union of leptotene threads takes place here also." 



Browne ('13), from a comparative study of the spermatogenesis of 

 three species of Notonecta, regards the evidence, though not abso- 

 lutely conclusive, as indicating a conjugation by parasynapsis. 

 Kornhauser ('14), as a result of a very careful study of the spermato- 

 genesis of two species of Enchenopa, finds conclusive evidence of a 

 parasynaptic union at the beginning of the growth-period. The 

 evidence for parasynapsis in the Hemiptera is thus seen to be very 

 strong. 



