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 Arc si- 

 tuated upon the side of the body in the spot in which we see them 

 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 '' Museum '^ 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 f 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 cannot hinder us believing the pretended inhabitants of the 

 spermatic liquor in the Anodontes, the Ascidia, 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. 1 believe that Trembley had observed, towards the middle of the last 

 century, that Ilydrcs in a glass of water wandered to the side of tlie glass 

 whence the light came. 



t Journal I'lnstitut, 1845, p. 167. 

 Ann. ^ May. N. Hist. Vol. xyii. T 



