Miscellaneous. 143 



Lerneopoda) i:he division of the ovary into germigene and vitellogene 

 does not exist ; but this organ is formed of a ramified tube, of which 

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

 characters of which are identical with those of the protoplasmic 

 cords of Clavella and Com/ericola. If the walls of the ovary are torn, 

 a great number of eggs are set at lihertg, each of which bears at one 

 of its poles a fragment of 2^rotoplasTnic cord formed of piled-up 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 was 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 Saccidinre 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. 



1)1 studying the first phases of the embryonic development of the 

 Sacculinse, / have ascertained that these animals present at first the 

 complete segmentation of the vitellus. Now, as I have shown in a 

 previous memoir, the complete segmentation of the vitellus only 

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

 suspension in the protoplasm of the ovicell, 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 divi- 

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

 expense of the cicatricula exclusively. But in the Saccidina'. the 

 Avhole 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 vitellns. The protoplasm of the 

 four segments, carrying with it their nuclei, moves to one of the po'es 

 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 are 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 conslitute the four 

 first embryonic cells, in the form of little proioplasmic 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- 



