Miscellaneouft. 143 



Lerneopoda) the division of the ovary into germigene and vite]logeii« 

 does not exist ; but tliis organ is formed of a raiuiticd tube, of which 

 all the branches are tilled with fragments of protoplasmic cords, the 

 characters of which arc identical with those of the protoplasmic 

 cords of Clavella and Comjerkohi. If the walls of the ovary are torn, 

 a gretit number of eyt/s are set at Uherty, each of ivhiih hears at one 

 of Its poles a fragment of protoplasmic cord formed of piled-tip dis- 

 coidal cells. When the eggs have arrived at maturity they separate 

 from the cord, are ejected, and it is the cell of the protoplasmic 

 cord which wa-s immediately adjacent to the egg that increases, 

 becomes filled with refractive elements, and becomes in its turn an 

 egg. It is impossible not to recognize that these eggs, bearing at 

 one of their poles a fragment of ovarian cord, are really the ana- 

 logues of the eggs of the Saccidiwe provided with a polar cell. The 

 polar cell represents anatomically and physiologically the fragment 

 of the protoplasmic cord of Anchorella and Lerneopoda, which sepa- 

 rates, like it, from the mature egg to furnish new eggs. 



In studyintj the Jirst jthases of the emhri/onic development of the 

 Sacculinae, / have ascertained that these animals present at Jirst the 

 comjilete segmentation of tJie vitellus. Now, as I have shown in a 

 previous memoir, the complet-e segmentation of the \-itellus only 

 takes place when the whole mass of the nutritive elements occurs in 

 suspension in the protoplasm of the oviccll, which excludes the 

 idea of a cicatricula, A cicatricula exists when a great part of the 

 nutritive elements is outside the protoplasm of the ovicell, as in 

 birds. In this case these elements do not take part in the di\-i- 

 sion of the ovicell, and the segmentation is partial ; it occurs at the 

 expense of the cicatricula exclusively. But in the Saccidincp the 

 whole mass of the vitellus becomes divided into two equal portions, 

 in consequence of the formation, all round the small section of the 

 egg, of a furrow which starts from the periphery and advances gra- 

 dually towards the centre. Soon afterwards a new furrow appears 

 on the surface of the vitellus, crossing at a right angle that which 

 had first appeared. The mass of the vitellus is thenceforward di- 

 vided into four portions ; they have each the form of a quarter of 

 an ellipsoid which has been divided by two perpendicular planes 

 both passing through the centre. From this moment in each of the 

 four segments a separation takes place between the protoplasmic ele- 

 ment and the nutritive elements of the vitellus. The protoplasm of the 

 four segments, carrying with it their nuclei, moves to one of the poles 

 of the egg, which is the extremity of the diameter in which the two 

 planes intersect. We see the four segments become more and more 

 clear at this point, and free themselves completely from the nutri- 

 tive elements, which arc driven to the opposite poles. Then the 

 clear parts, each provided with a nucleus, are separated by a furrow 

 from the darker portion of the segment ; they constitute the four 

 first embryonic cells, in the form of little protoplasmic globes, each 

 provided with a nucleus. The four large dark spheres, formed of 

 very refractive elements, no longer represent cells; they will also 

 become fused together, so as to form a single mass of nutritive ele- 



