THE SPERMATOGENESIS OF THE SPIDER. 



WITH PLATES IX. AND X. 

 LOUISE BAIRD WALLACE. 



About four years ago, when the present work was undertaken, 

 several investigators had described a peculiar chromosome in in- 

 sect spermatogenesis, but outside of the insects it had not then 

 been reported and it was a matter of considerable interest to dis- 

 cover whether or not it obtained generally in the maturation of 

 the germ cells of the Arthropoda. Since Dr. Montgomery had 

 failed to find it in Pcripatns, he suggested to me the advisability 

 of trying some higher form. A study of the reproductive organs 

 of Liinulns was first attempted but these proved unfavorable on 

 account of the minuteness of the cells. The testes of the spider 

 were then examined and were found to be promising material 

 for, as an offset to the rather large number of chromosomes 

 characteristic of the Arachnida, the germ cells are of fairly good 

 size and the peculiar chromosome forms a conspicuous structure 

 of the cell even to a casual observer. 



For various reasons the common tube- weaving spider, Agalena 

 n<zvia, has been taken as the basis for work, but a comparative 

 study of a few representatives from the Drassidae, Attidae, Lyco- 

 sidae, Therididse and Epeiridae was found of great value in the 

 interpretation of some points. After the publication of a brief 

 preliminary in the fall of 1900, the problem was laid aside until 

 the fall of 1903, when it was resumed at the University of Penn- 

 sylvania uuder the direction of Dr. E. G. Conklin. It gives me 

 pleasure to cordially express my indebtedness to Dr. Conklin for 

 his ever ready encouragement and helpful criticism throughout 

 the year. 



METHOD. 



By almost common consent the strong solutions of Flem- 

 ming's chromo-aceto-osmic mixture and Hermann's platino-aceto- 

 osmic mixture have been chosen as giving the finest fixation for 

 work in spermatogenesis and while I have used a number of dif- 

 ferent fluids, I can add my testimony to the superiority of the 



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