414 Avery E. Lambert. 



lent papers have been published which show that the trend of observa- 

 tion, in recent years, has been in that direction. 



The earliest studies on the embryology of the Araneina were 

 undertaken before the technical methods, now employed in such 

 investigations, were known. For this reason, the earliest papers 

 on the subject have little value for us apart from their historical 

 interest. 



The earliest paper to deal distinctively with the development of 

 the spider was published by Herold (15) in 1824. In 18G2 

 Claparede (8) published the results of his studies on the earlier 

 stages in the development of the spider. His observations were made 

 with surface preparations only, and consequently failed to throw 

 light on the segmentation of the nucleus and the formation of the 

 germ layers. 



He succeeded, however, in carrying his studies of the develop- 

 ment of the external form of the embryo up to the period of rever- 

 sion. He observed and figured the caudal thickening, to which he 

 gave the name "primitive cumulus." This term has not been con- 

 sistently applied, by those who have subsequently treated the sub- 

 ject, to the accumulation of cells which form a slight elevation in the 

 caudal region of the embryo ; but has been more commonly used to 

 designate the first accumulation of cells which occurs in the middle 

 region of the blastodisc. 



The division of the yolk of the spider's eggs into columns, and the 

 subsequent arrangement of these columns in the form of ''rosettes,"^ 

 was correctly reported by Ludwig (24) in his study of the forma- 

 tion of the blastoderm of spiders' eggs, published in 1878. He also 

 noted the fact that the l)lastoderm arises at one end, instead of cover- 

 ing the entire egg. 



In 18Y8, Barrios (3) published the results of his study of the 

 development of the spider in which he called attention to what he 

 termed a ''limnloid" stage, referring to the form of the embryo ])revi- 

 ous to the period of reversion. 



Up to this time investigators had to content themselves with the 

 study of the external form of Araneid embryos. Balfour (1), who 

 first applied the section method to the study of Arachnid embryology, 



