304 Miscellaneous. 



the SacndiiKP is constructed upon n typo analogous to thai of Kirds ; 

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

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

 fest especially in the young ovules, which even ai)pear as if composed 

 of two distinct halves or lobes sei)aratrd by a median constriction, of 

 which one represents the primitive yelk, the other the germiiiative 

 portion. Afterwards the latter is no longer \-isible, except in the form 

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

 The yelk and the cicatrieula 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 o\'ule, M. 

 Gerbc regards the ve.sicle ])laced at the centre of the cicatrieula 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 Araclinida, Myriopoda, «S:c. 



When M, Gerbe published these residts I thought it necessary to 

 raise some objections to his views; but not having then any personal 

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

 to showing that his observations had not the precision neces.sary to 

 justify the general conclusions which M. Gerbc drew from them 

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

 ovum. I have since acquired more decisive proofs, ha\"ing had the 

 opportunity, during a recent residence on the coast, of undertaking 

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

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

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

 M. van Beneden, I am obliged to interpret them quite differentlj* 

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

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

 neden, although made quite independently. This will appear clearly 

 from the following re<inne of my investigation of Peltorjaster Parfuri 

 (Rathke). 



Let us first examine the facts observed in the little Naupliiform 

 larva> which represent the first 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 globules, the remains of the 

 nutritive vitellus, and of larger l)odies, refracting light much more 

 feebly, and ha\-ing all the characters of true ccUs. But on bursting 

 the outer integument of the larva by careful pressure, the content-s 

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

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

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

 budding. This structure of the ovary of the larva of Pdtor/aster 

 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 imj)crceptible 

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

 stitution of thesf })odi('S recalls the organization which M. Gerbc 



