XVII. NOTES ON THE DEVELOPMENT OF THE ARANEINA*. 



(With Plates 30, 31, 32.) 



THE following observations do not profess to contain a 

 complete history of the development even of a single species 

 of spider. They are the result of investigations carried on at 

 intervals during rather more than two years, on the ova of 

 Agclena labyrintJiica ; and I should not have published them 

 now, if I had any hope of being able to complete them before 

 the appearance of the work I am in the course of publishing 

 on Comparative Embryology. It appeared to me, however, 

 desirable to publish in full such parts of my observations as 

 are completed before the appearance of my treatise, since the 

 account of the development of the Araneina is mainly founded 

 upon them. 



My investigations on the germinal layers and organs have 

 been chiefly conducted by means of sections. To prepare the 

 embryos for sections, I employed the. valuable method first 

 made known by Bobretzky. I hardened the embryos in bichro- 

 mate of potash, after placing them for a short time in nearly 

 boiling water. They were stained as a whole with haematoxylin 

 after the removal of the membranes, and embedded for cutting 

 in coagulated albumen. 



The number of investigators who have studied the develop- 

 ment of spiders is inconsiderable. A list of them is given at 

 the end of the paper. 



The earliest writer on the subject is Herold (No. 4) ; he was 

 followed after a very considerable interval of time by Claparede 



1 From the Quartei'ly Joitrn. of Microscopical Science, Vol. xx. 1880. 



