230 
ALFRED GIARD. 
eight cells; it is very difficult to count with exactitude, 
since optical sections rarely present themselves, and it is 
impossible to make real sections. 
The ectodermal cells present very long and very dense 
cilia. By using osmic acid, followed by picrocarmine, it is 
easy to preserve the ectoderm with its clothing of cilia. 
Preparations made a year ago give at this day an excellent 
idea of the living animal.^ 
The endoderm is primitively formed of larger cells than 
those of the ectoderm, but they undergo in the adult a very 
singular modification. The whole of this layer forms an 
oval sac, the anterior extremity of which is hidden by the 
papilliferous ring, and extends from the penultimate meta- 
mere until it is inserted, in the form of a sort of pedicle, 
between the four terminal ectodermal cells (Plate XXII, 
figs. 3 and 4). The swollen part of the endodermal sac 
presents, when examined with the immersion lens, fine mus- 
cular bands disposed in a finely granular matrix, and recall- 
ing the appearance of the endodermic muscular layer of 
certain nematoids. 
I do not believe that these muscular elements are derived 
from the bodily transformation of certain endodermal cells ; 
I consider them rather as a part only of such cells, which are 
thus called upon to play a double physiological role. They 
would thus be analogous to the epithelio-muscular cells 
described by Korotneff in Hydra, but with this difference, 
that in the present case it is the external part of the cell 
which becomes muscular, the internal part remaining 
epithelial. 
I would draw the attention of histologists, more skilled 
than I am in technical methods, to this very delicate point. 
The question involved is one worthy of their skill. 
Metschnikoff has recently put forward the opinion that 
the striated bands are formed by the tails of spermatozoa, 
the entire endoderm being nothing but a testicular gland.^ 
1 am quite unable at present to accept the opinion of my 
learned opponent. These bands are chiefly visible in young 
individuals; their number is constant; they are always 
disposed obliquely, as I have figured them, on an ovoid 
endoderm ; and this disposition is not, as I had at first 
supposed, the result of an accidental torsion. On changing 
the point of view, the continuation of the spiral is seen 
* I have shown these preparations to various persons, and specially 
to Dr. Macleod, of the University of Ghent, who spent a few days at 
Wimereux during last April. 
2 ‘ Zoologischen Anzeiger/ II, No. 43, p. 619. 
