Procopluilic Lobes of Epeira Cinerca. 415 



published a paper in 1880 which contained several important con- 

 tributions to the knowledge of the subject. 



Owing to his failure to obtain sections of the pre-blastodermic 

 stages he was led to attribute the formation of the mesoderm, in part, 

 to cells which, he believed, migrated into this layer from the yolk. 

 He observed, however, and correctly reported, that a portion of the 

 mesoderm is derived from the blastoderm. 



Schimkewitsch (38), in a paper published in 1887, maintained 

 that all of the cells derived from the division of the segmentation 

 nucleus do not migi-ate to the surface of the egg, but some remain 

 in the yolk and contribute to the formation of the cndoderm; this 

 conclusion later researches have failed to confirm. But this author 

 w^as able to demonstrate that the rostrum, in spiders, arises as a pair 

 of prominences on the anterior margin of the cephalic plate, these 

 prominences uniting later to form the upper lip. 



Morin (30) in a brief paper which appeared in 1886 followed the 

 whole course of the development of the spider. Tn his study of the 

 fate of the seginentation nucleus, he found that the nuclei, resulting 

 from its division, rise to the surface of the egg, the greater number 

 of them participating in the formation of the blastoderm. Accord- 

 ing to this author, the cells which appear in the yolk, after the forma- 

 tion of the first cellular layer, are not derived from cells that have 

 been retained in the yolk, as had been stated by previous authors, but 

 from the blastoderm itself. 



The two most important contril)utions to the study of the embry- 

 ology of the spider, and in many respects the most satisfactory, are 

 those wdiich were made by Locy (23) in 1886, and Kishinouye (19) 

 in 1890. Locy made a oom]ilete study of the embryology of Agalena 

 naevia by the section inctliod. lie established the fact that a depres- 

 sion exists in the middle region of the primitive cumnlns, beneath 

 which the multiplication of cells takes place very rapidly. Because 

 of the relation which this depression bears to the mass of rapidly 

 proliferating cells, he interpreted it as representing the blastopore. 



The most imi)ortant pnrf of Locy's work is that which relates to 

 the development of the anterior median eyes. He was able to show 

 that these eyes arise by means of an infolding which causes an inver- 



