140 



MISCELLANEOUS. 



Ujion the Mode of Formation of the Egg and the Embryonic Develop- 

 ment of the Sacculinse. By M. E. tan Beneden. 



In a note inserted iu the ' Comptcs Rendus ' of the month of 

 Pebruaiy last (February 22, 1S69), M. Gerbe has given the results 

 of his researches upon the constitution and development of the 

 ovarian egg of the iSacculince. According to this avthor, the ovules 

 are formed at their first appearance of two transparent cells closely 

 applied to each other, each provided with a vesicular nucleus and a 

 common membrane (vitelline membrane). One of these cells in- 

 creases considerably, there are developed iu it a large quantity of 

 refractive globules ; whilst the other remains small and only acquires 

 a few fine globules ; and when the egg is mature, the large cell, in 

 which the elements of the yolk are developed, has attained such a 

 predominance that the other lobe, of which the development has 

 remained in some sort stationary, only represents a small, scarcely 

 perceptible eminence upon one of the poles of the ovule. M. Gerbe 

 regards the large cell as giving origin to the vitellus, and com- 

 pares it to the yolk of the egg of birds ; whilst the little cell, in his 

 opinion, represents the germ or cicatricuhi. Moreover M. Gerbe 

 thinks he finds in the development of the ovum of the Sacculinse the 

 exjilanation of the physiological part performed iu the egg by that 

 body which Von Wittich, Von Siebold, and V. Carus have described 

 in the egg of several spiders, by the side of the vesicle of Piirkinje, 

 and which M. Balbiani has observed in certain Myriopods. One of 

 the two cell-nuclei of the primitive bilobed ovule of the Sacculinae 

 would be the nuclens of the formative cell of the vitellus and the 

 homologue of the vitelline nucleus of the egg of the spiders ; the 

 other would be the germinative nucleus or the nucleus of the germ- 

 cell, the homologue of the germinal vesicle of the egg of the spiders 

 and Myriopods. 



The observations which I have made upon the development of the 

 ovarian egg of the 8acculince agree, in certain points, with those of 

 the learned embryogenist of the College of France ; but the inter- 

 pretation which I have given to the facts is essentially different, 

 which is due to the circumstance that, upon some points, I am not 

 able to confirm the investigations of M. Gerbe, and that some im- 

 portant facts have escaped his attention. 



The ovules are not, at their first appearance, formed of two cells 

 closely applied to each other ; they consist, at first, of a single cell, 

 formed of a perfectly transparent viscous matter (protoplasm) hold- 

 ing in suspension some globules which strongly refract the light, 

 and of a vesicular nucleus, with very delicate outlines, measuring 

 about half the diameter of the cell and provided with a single very 

 refractive nucleolus. The diameter of this cell is about 0-06 millim. 

 Along with these cells are seen others, which present an elongated 

 form and are provided with two nuclei, without, however, mani- 

 festing any tendency to the division of their bodies. Others, on the 



