74 Miscellaneous. 



the aperture of the ovaries opens. The fecundating elements of the 

 male are imprisoned in this sort of membranous sac ; and when, a 

 few moments afterwards, the eggs arrive in the same place, they 

 will find themselves bathed in a liquid very rich in spermato- 

 zoids. 



Each laying consists of five or six eggs, which the female retains 

 for a few minutes in the pouch above described ; then she quits the 

 bottom to go in search of a favourable spot for their evolution. Her 

 choice leads her in preference to a well-illuminated part, such as 

 the glass wall of the aquarium, or a stone that emerges from the 

 water ; with her mouth she cleans a place situated at least 10-15 

 centims. below the level of the water, then, applying her abdomen 

 to this place, she opens her sac and attaches the eggs, which adhere 

 by means of the viscosity with which they are endued. 



All the eggs being deposited, contact with the male recommences ; 

 and the ovipositions thus follow one another forty or fifty times in 

 the course of the day. I estimate the total number of eggs emitted 

 at about two hundred and fifty*. 



At the moment of deposition the eggs, arranged in groups of 

 from three to five, are of a milky white, and but slightly transpa- 

 rent ; they afterwards become yellowish, and at the moment of ex- 

 clusion, i. e. from the eighth to the tenth day of incubation, they 

 become blackish : this coloration is due to the pigment spots which 

 cover the body of the embryo. 



At the moment of its birth the embryo is globular. At first one 

 can only distinguish the four barbels ; the umbilical vesicle, which 

 is semitransparent, is not very voluminous ; the embryo holds itself 

 in the normal position, and not lying upon its side, like most embryos 

 of other fishes. Speedily the tail and the other fins appear. These 

 latter developments last on the average three days, during which 

 time these fishes lead an independent and isolated life. When this 

 period is past, i. e. from twelve to thirteen days after deposition, all 

 these young fishes collect together and move about the bottom of the 

 aquarium. 



The growth of this fish is not very rapid ; it does not become 

 adult until two years after its birth. 



An interesting fact is the change of the period of reproduction 

 presented by our CallkhtJujs. At La Plata it is in the months of 

 October and November that it breeds. After arriving in Europe 

 it passed a year without producing young. In 1878 oviposition 

 took place in August and September. The produce of this genera- 

 tion oviposited this year in the month of June. Evidently there 

 has been an adaptation to our cHmate, the temperatures of which 

 are the reverse of those of South America. — Coniptes Eeudiis, Dec. 6, 

 1880, p. 940. 



* The layings observed by me always commenced between 9 and 10 

 o'clock A.M., and terminated about 2 p.m. 



