ON THE DEVELOPMENT OF NEBALIA. 385 



Milne-Edwards (1828 and 1835) who found Nebalia on 

 the coast of Brittany, and described it under the name of 

 Nebalia Geoffroyi, after Geoffroi St. Hilaire, gave as his 

 reason for not placing it among the Malacostraca the fact 

 that the thoracic legs with their himeUate appendages do 

 resemble those of Branchipns, and these gills are in noway 

 like the gills of Decapods. In 1840he wi-ites of theNebalidee 

 " Elles semblent a plusieurs egards etablir le passage entre 

 les Mysis et les Apus/' but places them in the family "Les 

 Apusiens " among the Phyllopods. 



Kroyer (1847) (of whom I know only through Glaus and 

 Metschnikoff) stated that Nebalia could not be a Phyllopod 

 because it carried its embryos in the brood pouch till they 

 were practically adult. 



Metschnikoff, in 1868, published a long account of the 

 development of Nebalia. As this is an important paper of 

 which unfortunately there is no published translation from 

 the Russian, I give here a somewhat lengthy abstract of it. 

 I must first thank Miss Zelda Kahan for translating the paper 

 for me. 



Metschuikoff begins his account of the development by 

 describing the formation of the blastoderm. In this part I 

 will give his words as nearly as possible : " Before total seg- 

 mentation there is another division in the formative yolk, and 

 there appears a polar vesicle. Both of these appear on the 

 lower portion of the egg. Here there is formed a small 

 accumulation of colourless protoplasm containing a large 

 number of granules. This protoplasm, which is nothing more 

 than generative yolk, separates itself from the egg envelope, 

 and thus there comes into existence a small space between the 

 shell and the yolk. In this space there appears a small 

 globule of protoplasm which plays no part in development 

 and soon disappears. 



" The further development depends on the increase in quan- 

 tity of the generative yolk. When it has increased so as to take 

 up about one fifth of the volume of the entire egg it divides 

 longitudinally into two parts oval in shape. These divide 



