302 Miscellaneous. 



On the Anatomy and Physiology of Amphioxus. 

 By M. P. Bert. 



The existence of Amj)hioxus has been ascertained, during the 

 month of March of this year, in the muddy sands of the basin of 

 Arcachon, by MM. Filhoux and Lafont. This is the first time, to 

 my knowledge, that any one has found it on the oceanic shores of 

 France. 



From March to May all the individuals have the generative organs 

 filled with eggs or with sjiermatozoids in diiferent degrees of develop- 

 ment. After this period these organs are empty and atrophied. 

 Like all fishes, the Amphioxi are fit for reproduction before they 

 have attained their full size. No difference can be ascertained be- 

 tween the male and female, even when the generative sacs are filled 

 with their products, except with the aid of magnifying-instruments. 

 The number of these pouches is, in both sexes, from twenty-two to 

 twenty-six ; that of the muscular masses is sixty-one pairs ; but 

 that of the branchial spaces varies considerably with the size, as has 

 long been known (an individual of the length of 20 millimetres has 

 93 spaces, one of 30 millimetres 153). This augmentation takes 

 place at the two extremities of the branchial apparatus ; of this we 

 may easily be assured by taking for point of reference the anterior 

 extremity of the liver, which always corresponds to the sixteenth 

 muscular mass. Beyond the abdominal pore the coats of the body 

 do not closely embrace the intestine, as ^I. de Quatrefages says. I 

 have, on the contrary, verified the assertion of J. JMiiller, who de- 

 scribes a prolongation of the peritoneal cavity going to the anus. 

 It is true that the particles which have traversed the branchial net- 

 work never get into this passage, which is sometimes obliterated by 

 the contractions of the coats of the body. On the other hand, I 

 cannot admit the existence of the lateral canal (prolongation of the 

 general cavity) which according to some anatomists opens at the side 

 of the mouth. 



Each of the ovarian sacs consists of a thin wall furnished with 

 pavement-epithelium, of which the very pale cells measure about 

 0*01 millim. Within, separated from the sac by an interval full of 

 a transparent liquid, is the ovigerous sac, which is extremely thin 

 and without epithelium when the eggs are developed ; but when 

 these first make their appearance, it possesses epithelial cells 0*0 10- 

 0*014 millim. These cells group themselves round the young 

 eggs, which appear to originate only in contact with the wall. The 

 smallest that 1 have seen were 0-038 millim., their germinal vesicle 

 0*009 milhm., and their germinal spot 0*004 millim. I have found 

 them in the same sac from that size to 0*24 millim., which is that of 

 the mature egg (vesicle 0*09, spot 0*026 millim.). The vitellus 

 becomes opaque when the egg attains 0*085 millim. I have seen at 

 the same time in the sac some isolated corpuscles which had all the 

 characteristics of the germinal vesicle. When the eggs are mature, 

 they lose their spot and vesicle, and, being compressed in the sac, form 

 at its surface an elegant mosaic. They then emerge by the burst- 

 ing of the sac and pouch : in the wall of the former some pigment- 

 granules are developed ; it then contracts and becomes invisible. 



