382 Scientific Intelligence — Zoology, 



every two or six minutes, according to the temperature or vitality of 

 individuals. In the Klopodes and Glauconus, the movements of this 

 vesicle exactly imitate those of the heart ; they are very close 

 upon one another, and the organ dilates and fills instantaneously 

 with sanguineous fluid. The contractions take place every 7 to 10 

 seconds, at a temperature of 20° C. 



M. Pouchet's observations have been made on the following spe- 

 cies ; — Vorticella infusiorum, Duj. ; Klopoda cucullus, Muld. ; 

 Glaucoma scintillans, Ehr. ; Dileptas folium, Duj. — (L' Institute 

 25th November 1848, p. 349.) 



8. Artificial Fecundation of the Ova of Fishes. By M. A. de 

 Quatrefages. — The remarkable fecundity of fishes is well known. 

 By the researches of different authors, it has been ascertained that a 

 perch, of medium size, contains 69,216 ova; a pike, of 10 kilo- 

 grammes, has afforded 166,400; 167,400 have been counted in a 

 carp weighing a little more than 1 kilogramme, and 621,600 in 

 another individual of the same species which weighed 4^ kilogrammes. 

 Rousseau gives 7,635,200 as the number of ova in a sturgeon, and 

 Leuwenhoeck has reckoned as many as 9,344,000 in a single had- 

 dock. 



Looking at these figures it is natural to ask, how it happens that 

 the number of fishes is not more considerable. This may, per- 

 haps, be explained by taking into account the circumstances which 

 prevent the development of these myriads of germs. We know that, 

 in the greater number of fishes, there is no copulation. At the time 

 of spawning, it is true, the males and females alike seek for localities 

 suited for the development of their ova; but the latter are deposited, 

 and the fecundating liquid emitted, without any union of the sexes 

 to secure the contact of these two elements. Fecundation is quite ac- 

 cidental, and, consequently, a great number of ova perish without 

 being fecundated. Besides, the spawn of the females is very often 

 devoured at the very moment of depovsition, either by voracious fishes, 

 or by the parents themselves. Lastly, the spawn laid near the banks, 

 in rivers and ponds, very often perishes, by being left dry in conse- 

 quence of the waters retiring from them. 



Artificial fecundations would remove all these causes of the de- 

 struction of the ova, and the practice to this method presents no diffi- 

 culty. It is sufficient to place the ripe roe of a certain number of 

 females in some vessel along with a quantity of water sufficient to 

 allow the ova to float freely when the liquid is shaken, then to press 

 out the milk of the male into this vessel. In a few instants, if the 

 ova have reached their term, and the fecundating liquid be sufficiently 

 elaborated, fecundation will be completed ; all the ova will be fecun- 

 dated. We know that fishes, experimented upon in this way, fulfil 

 these conditions, for, by pressing the abdomen slightly from before 

 backwards, wo can easily squeeze out the contents of the reproduc- 

 tive organs. The ova once fecundated, ought to be placed in a situ- 

 tion proper for their development, and here precautions are required 



