M. Van Beneden on the Physiology of the Simple Ascidians. 249 
other organ of a special sense. I have ascertained the existence 
of eyes in one species in its adult condition, at the end and all 
round each of the tubes; and in its embryons, other eyes are si- 
tuated upon the side of the body in the spot in which we see thm 
in other animals of the same form. ‘The latter disappear with 
its nomade life. Milne Edwards has seen some black specks in 
the fry of the compound Ascidians, but he has not assigned them 
a function. This is the first ascertained instance of an animal 
having two kinds of eyes—the one for the embryonic period, the 
other for the adult and perfect estate*. 
In the anatomical section I have been able to complete what 
was known of the reproductive system. Milne. Edwards had de- 
termined the existence of the male and female organ in the same 
individual, but the learned professor of the ‘‘ Muséum ” avows 
that he could not discover in what way the eggs and the sper- 
matozoa were ejected. That gap I have also filled up. I have 
found a species, which, from the transparency of its parietes, was 
a favourable subject for observation; and I have seen that in it 
there were several outlets for the passage of the spermatic fluid 
into the cloacum, but one oviduct only for the exclusive passage 
of the eggs. The hypothesis which had been made in reference 
to this subject has not been confirmed. 
Notwithstanding the assertions to the contrary} of the phy- 
siologist who, quite recently, has obtained such an honourable 
distinction from the Academy of Sciences of Paris, I more than 
ever persist in my belief that the spermatozoides are analogous 
to the globules of blood: I cannot consider them as animalcules, 
nor consequently as organized beings. I have not yet had an 
opportunity of studying the spermatozoides of the Tritons, but 
that eannot hinder us believing the pretended inhabitants of the 
spermatic liquor in the Anodontes, the Ascidie, the Bryozoa, and 
other inferior animals in which we have observed them, to be free 
cellules, and usually or always vibrating. It is not by inductive 
reasoning that I have been led to this result, as M. Pouchet thinks, 
* There still exists a prejudice in science,—a prejudice born of the ana- 
tomy of the superior animals,—that an animal cannot be sensible of the light 
without eyes, that eyes necessarily require the existence of an optic nerve, 
and that where this nerve exists there must also be a brain or cerebral gan- 
glion. The study of the inferior animals has completely overturned this 
error. In fact, it ought to have been perceived long ago that the Hydra 
and many other inferior animals are sensitive to light, moving freely and 
spontaneously, and fulfilling all the functions of relative and conservative 
life, and that too without eyes, without nerves, without muscles and without 
brain. I believe that Trembley had observed, towards the middle of the last 
century, that Hydre in a glass of water wandered to the side of the glass 
whence the light came. 
+ Journal l'Institut, 1845, p. 167. 
Ann. & Mag. N. Hist. Vol. xvii. T 
