12 MM. Kowalevsky and Barrois on Anchinia. 
elongated, and represents by itself the whole of the posterior 
branch besides a portion of the anterior ; at this stage it also 
presents an inflated portion, which afterwards disappears and 
does not exist in the adult. 
The ovary, the testis, and the disseminated cells (of the 
kidney ?) are more distinct from each other, and begin to be 
clearly recognizable. 
Finally the margins of the incurrent and excurrent aper- 
tures begin te thicken in order to form papillae, while over 
the rest of the body, especially at the level of the endostyle 
and of the nervous ganglion, the epidermis becomes consider- 
ably reduced in thickness. 
5. In the state represented by fig. 7 the bud has lost all its 
embryonic character and acquired an aspect which absolutely 
resembles that of the adult; the summit of the body is no 
longer occupied by the nervous ganglion, but by the spiral 
organ (as 1s shown in fig. 1. 7-8, and fig. 7); the general 
aspect has completely changed; the cells which form the 
external lamine as well as the pharyngeal and cloacal sacs 
have acquired the flat form which they present in the adult ; 
and the general transparency has become very great; the 
pharyngeal sac has considerably increased; the endostyle 
has lost its inflated form to acquire an aspect approaching that 
of its definitive form; and, lastly, the whole region of the 
genital mass has been reduced in such a manner that the 
peduncle, instead of retaining its original direction, is now 
directed downward, occupying a position absolutely different 
from its previous one and much nearer to the heart. It is 
this last alteration especially that modifies the general aspect 
presented by the bud and gives it an absolutely different 
form. 
The internal organs have also undergone modifications of 
some importance. Of the two muscles which bounded each 
of the apertures (incurrent and excurrent) the posterior one is 
now further from the aperture, and the anterior one alone 
borders it closely. Further, the thickened margin of the 
posterior aperture begins to be recurved at its upper part to 
form a sort of hook, into which the muscle penetrates, and 
which is the commencement of the long filament that occupies 
this position in the adult. 
The branchia has become elongated and recurved, as 
shown in the figure; but the branchial fissures are only 
slightly lengthened. 
The intestine has continued to be developed in the direction 
already indicated in the preceding stage; but the kind of 
cecum formed previously (cw) at its lower part has disap- 
