304 Miscellaneous. 



the Saccidina is constructed upon a type analogous to that of Birds : 

 that is to say, it is composed of a nutritive part, or yelk, and a 

 plastic part, or cicatricula. According to him, this structure is mani- 

 fest especially in the young ovules, which even appear as if composed 

 of two distinct halves or lobes separated by a median constriction, of 

 which one represents the primitive yelk, the other the germinative 

 portion. Afterwards the latter is no longer visible, except in the form 

 of a small rounded prominence on the surface of the mature ovum. 

 The yelk and the cicatricula each bear at the centre of formation a se- 

 parate vesicle, such as I had myself previously assumed for the ova of 

 a considerable number of animals ; but, reversing the parts ascribed 

 by me to each of these two constituent elements of the ovule, M. 

 Gerbe regards the vesicle placed at the centre of the cicatricula as 

 corresponding to the germinal vesicle of other species of animals, 

 and that situated in the midst of the yelk as the homologue of the 

 second vesicle which I have indicated in the vitelline nucleus of 

 the Arachnida, Myriopoda, &c. 



"When M. Gerbe published these results I thought it necessary to 

 raise some objections to his views; but not ha%"ing then any personal 

 knowledge of the facts upon which he based them, I confined myself 

 to showing that his observations had not the precision necessary to 

 justify the general conclusions which ^XI. Gerbe drew from them 

 with regard to the function of the two primitive vesicles of the 

 ovum. I have since acquired more decisive proofs, having had the 

 opportunity, dui'ing a recent residence on the coast, of undeitaking 

 some researches on my own account into the mode of formation of 

 the ovum in the SaccuJintP. I have observed all the interesting facts 

 to which !M. Gerbe first called the attention of naturalists ; but, like 

 M. van Beuedeu, I am obliged to interpret them quite differently 

 from the able naturalist of the College of France. On the contrary, 

 my observations agree in almost all points with those of AT. van Be- 

 neden. although made quite independently. This will appear clearly 

 from the following rhume of my investigation of Peltoijaster Paquri 

 (Rathke). 



Let us first examine the facts observed in the little Xaupliiform 

 larva; which represent the fii'st age of the animal at its escape from 

 the egg. When observed in an uninjured state, we only see in 

 their interior a mixture of refractive globtdes, the remains of the 

 nutritive vitellus, and of larger bodies, refracting light much more 

 feebly, and having all the characters of true cells. But on bursting 

 the outer integument of the larva by careful pressure, the contents 

 escape, and we see that these cells are rudimentarj' ova attached by 

 a prolongation, in the form of a peduncle, to a slender central cord, 

 a sort of rachis, on the surface of which the ovules originate by 

 budding. This structuxe of the ovary of the larva of Pdtof/oster 

 greatly reminds one of that of the same organ in the Arachnida. 

 The ovules are pyriform ; the largest have an average diameter of 

 0*025 millim. ; whilst the smallest appear as almost imperceptible 

 grains attached to the surface of the rachis. Nothing in the con- 

 stitution of these bodies recalls the organization which M. Gerbe 



