682 Queries and Answers, 



in their motions, and, when a female was about to shed her spawn, the 

 males (which were ten times as numerous as the females) crowded round 

 her in such a manner as to render it very difficult, if not impossible, to 

 speak with certainty on the subject. I will state what steps I took to satisfy 

 myself; and, perhaps, the history of my failure may be of use to future 

 observers. 



It occurred to me, from what I observed, that it was probable the males 

 had the power of absorbing the eggs after exclusion, and impregnating them 

 within their own bodies : and 1 caught a dozen males at different times 

 when they were attending on the female, and opened them, but I could 

 discover nothing like an egg. I then caught a female, and scattered the 

 spawn (which was expelled by the slightest pressure) in a place frequented 

 by a number of males, but they took no notice of it whatever. I after this 

 caught a female when she was surrounded by a number of males, and appa- 

 rently in the act of shedding her spawn, and examined whether the spawn 

 which 1 pressed from her body was impregnated j but it appeared perfectly 

 homogeneous, and so delicate in its texture, that it burst with the slightest 

 touch ; whilst in that which I picked up from among the gravel, where it 

 was scattered abundantly, the impregnation was visible with the assistance 

 of the microscope ; and it was so much tougher in its covering, as to bear 

 rolling about in my hand without injury. 



I then tried to impregnate the eggs mechanically ^ and applied a drop of 

 the spermatic fluid to the egg at the moment of exclusion ; and it certainly 

 appeared to me, in one instance, both to increase the size, and alter the 

 colour, of the eggs it was applied to : but I was not able to produce the 

 same effect so decidedly in any of my subsequent attempts to do so. 



My observations, which were often repeated, induce me to believe that 

 the egg is impregnated at the moment of exclusion ; and that two males 

 have (almost invariably) access to the female at the same time ; for I fre- 

 quently remarked, that, when a female came among a number of males, they 

 immediately pursued her: if she was not ready for shedding her spawn, 

 she made a very precipitate retreat ', but, if she was, she came boldly in 

 among them, and was immediately pressed closely by a male on each side ; 

 and, when they had been in that situation a short time, were superseded 

 by other two, who wedged themselves in between them and the female, 

 who appeared to treat all her lovers with the same kindness. 



One difficulty is, that the spermatic fluid mixes very readily with water ; 

 and I cannot imagine how its virtue is preserved*, if (as I suppose may be 

 the case) the egg is impregnated after exclusion : but I also think it pro- 

 bable that the ventral fins of the female serve to conduct this fluid to the 

 place where it is needed ; and the chemical affinity between it and the egg 

 may be sufficient to account for the impregnation. 



{P.S. July 21th. I tried to hatch some of the eggs which I had en- 

 deavoured to fecundate. The attempt was unsuccessful. I placed the 

 eggs (which I had put into some clean washed gravel in a shallow vessel, 

 open at the top, and with holes drilled through the sides) in a small stream 

 of water; but 1 found, to my great mortification, on looking for them a day 

 or two after, that there was not one left, but that in their stead were many 

 aquatic insects, which had, no doubt, feasted on them as long as they 



* It appears to be a beautiful provision of nature that mixture with 

 water should increase the sphere of its action. Spallanzani found by 

 actual experiment that three grains of the seed of a male frog might be 

 diluted with a pint of water, without destroying its stimulating power. 



For an interesting series of experiments on this subject, see his Dissert- 

 ations ^ vol. ii. p. 142. chap. 3. — S. T. P. July 9. 1832. 



