198 Dr. J. Barrois on the 



Before approaching the special subject of my memoir I will 

 say a few words as to the formation of the blastoderm. 



Since Balbiani's memoir, Ludwig has published a very 

 complete treatise upon this subject : I adopt most of the 

 results of this author ; but there are some observations which 

 I must offer. Ludwig has asserted that the granular layer 

 placed by Balbiani at the surface of the vitellus (couche plas- 

 tique of Balbiani) really belonged to the vitelline membrane ; 

 I must declare myself against this assertion. I have, in fact, 

 found over the vitelline membrane a special layer not de- 

 scribed by Balbiani, to which, as Ludwig says, is due the net- 

 work that we observe at the surface of the ovum : it is not 

 formed by a continuous layer of juxtaposed globules, but only 

 of globules arranged in lines which intercross to form a kind 

 of net, in the meshes of which the vitelline membrane is un- 

 covered ; the whole appears most distinctly in the ova of 

 Epeira diadema treated with nitrate of silver. Independently 

 of this reticulated layer, I further distinguish, like Balbiani, 

 the formative globules of the cells of the blastoderm. These 

 sometimes acquire large dimensions, and present great regu- 

 larity ; one cannot mistake their identity with the elements 

 described by Balbiani when one observes the ova of Tege- 

 naria domestica. 



I therefore regard the description given by Balbiani of the 

 granules of the plastic layer as perfectly correct, and am of 

 opinion that this observer has done good service by drawing 

 attention to the strongly granular character of the protoplasm 

 in the Spiders ; but I adhere rather to Ludwig as regards the 

 distribution of these protoplasmic elements. I have never 

 seen them form a continuous layer at the surface of the ovum, 

 nor divide up into germinative areas ; but I see them con- 

 stantly appear in the form of trains or series between the 

 vitelline globules of the surface. Ludwig's deutoplasm- 

 columns (Deutojjlasmasdulen) are generally to be recognized 

 without difficulty ; but I have not been able to see them in 

 all the species — which, without invalidating the description 

 given by Ludwig, leads me to doubt the absolute necessity of 

 a regular arrangement of the masses of deutoplasm. There 

 may be a greater condensation of the embryogeny in cer- 

 tain species, so as to arrive at such a distribution of the pro- 

 toplasm, but without such a complete fusion of the masses 

 of deutoplasm into deutoplasm-columns — which would carry 

 back the essential characters of the formation of the blasto- 

 derm to the strongly granulated character of the protoplasm, 

 and to its first appearance between the vitelline globules of 

 the surface. 



