THE SPERMATOGENESIS OF AGALENA X.EVIA. 121 



Outside of the insects and myriapods, heterochromosomes have 

 been reported in the Araneina only and as yet this unusually 

 beautiful and interesting material has not only been comparatively 

 neglected, but there has been marked discrepancy in the results 

 of the few who have worked upon it. So far as I know, the only 

 published work upon the development of the male germ cells of 

 spiders which has been done under sufficiently modern methods 

 of technique to be of value to us here is that of Wagner in 1896, 

 myself in 1900, Montgomery, Bosenberg and myself in 1905 

 and Berry in 1906. With the hope of harmonizing the results 

 of the above-mentioned authors and of correcting and expanding 

 my own earlier results the present work was undertaken. It has 

 seemed best to use the common tube-weaving spider, Agalena 

 n&via, again as the basis of investigation, although a number of 

 genera have been studied in order to illustrate some points. 

 While my former conclusions in regard to the behavior of the 

 ordinary chromosomes are now only verified and strengthened, 

 those upon the distribution of the accessory chromosomes and 

 upon the nature of the degenerating cells need considerable re- 

 vision. After a careful reading of the literature on the subject 

 and after an examination of testes in various genera, I am con- 

 vinced that before long generalizations can be made in spider 

 spermatogenesis and that contradictions are mainly due to differ- 

 ences in observations and interpretations ; not to radical differ- 

 ences existing in the developmental history of the germ cells 

 themselves. 



My investigations were carried on in the Zoological Laboratory 

 of the University of Pennsylvania and it gives me pleasure to 

 warmly express my indebtedness to Professor Conklin for the 

 kind interest with which he has followed the progress of my work 

 and his helpful suggestions and encouragement. 



MATERIAL. 



Most of my material was collected in the state of Massachusetts 

 Where the breeding season of Agalena does not begin, usually, 

 until the last week of August and continues until late in Sep- 

 tember. In mid-summer the testes are largely made up of pri- 

 mary spermatocytes in the growth period while in May and the 



