SPERMATOGENESIS OF THE DRAGON-FLY. 287 



elongated form of the insect spermatozoa and may be divided 

 into two classes: 



1. In the genera Agrion, ^Eschna and Diastatomma, they are 

 fine, capilliform and extremely motile. 



2. In the genus LibeUnla he affirms they are more solid and 

 rod-like, and remain inactive in the male and even in the female 

 after fertilization. 



In all genera, the spermatozoa develop in the testis in bundles 

 surrounded by delicate sheaths. In JEsclina ocellata these 

 bundles are so large that they can be recognized with the naked 

 eye as white dots in the testis. In group (I) the bundles are 

 round or oval and somewhat compressed. Before the maturation 

 of the spermatozoa in the cyst surrounded by a sheath, there is a 

 big vesicular area which enlarges and becomes finely granular. 

 This is the beginning of the formation of the spermatozoa which 

 arise within the bladder-like area of the cyst. 



Von Siebold was uncertain as to the immobility of the sperma- 

 tozoa in the Libellula for he says, "Ob diese Spermatozoen unter 

 gewissen Bedingungen, welche mir entgangen sind, sich nicht 

 dennoch bewegen solten, weiss ich nicht zu sagen." 



Biitschli worked out a number of the developmental stages of 

 the head of the spermatozoon of Agrion puella. He described 

 the nucleus as sending forth a small elongation which increases 

 in length and forms an opaque head-spine. In an immature 

 spermatozoon, it measured o.oi to 0.045 mm. in length while 

 in the ripe spermatozoon it was reduced to .0078 to .009 mm. 

 He thought that there must be some deception in his results, 

 but in Sympetrum the same thing occurs. 



Lefevre and McGill (1908) extended and corrected the earlier 

 paper (1904) of McGill on Anax junius. The spermatogonial 

 number was found to be twenty-seven. The small or m chromo- 

 somes of the spermatogonium divided at both mitoses and was 

 distinct from the accessory which was a larger chromosome in 

 the spermatogonial group. A condensed chromosome-like body 

 persisting through the various growth stages was identified as 

 the odd or heterotropic chromosome of the maturation division. 

 They also found evidence which suggested that the synapsis 

 might be a side to side union of the threads instead of end to 

 end as first described. 



