How to obtain it. 197 



latter being attached to their broadsides. Some have one head 

 but two tails, and occasionally two fish have only one umbilical 

 sac between them. A rarer occurrence is to find one possessing 

 three heads, and rarer still three heads and three bodies with only 

 one tail. None of these live to grow up. They usually die soon 

 after the absorption -of the " sac," and although many persons 

 have tried to rear them, no one, as far as I know, has yet 

 succeeded in doing so, with the exception of an occasional cripple, 

 whose body has not been very seriously deformed. I have, at the 

 time I write, one of these moderately-deformed fish which I 

 succeeded in rearing, and which has been spawned for four seasons 

 in succession. The malformation does not appear to be hereditary 

 in this case, and the specimen is a brook trout ( Salmo fario). I 

 had two fish amongst a batch of American trout, a few years ago,, 

 which had abnormally large rounded bodies. They happened to 

 be a pair, and the eggs were duly taken from the one and 

 impregnated with milt from the other. The young fish were care- 

 fully watched, but no sign of the deformity of the parents was 

 visible amongst them. 



A few alevins will probably be noticed at or near the lower 

 end of the hatching box that have distended umbilical sacs, the 

 part affected looking almost colourless and transparent. There is,, 

 in fact, a clear watery fluid, which is discharged, or partially so, on 

 a puncture being made in the outer sac. The umbilical vesicle 

 really consists of two sacs, one inside the other. The inner sac 

 grows less as its contents are absorbed, but the outer one has not 

 the same contractile power. It can be punctured, however, 

 without apparently causing any pain to the fish, but the inner one 

 is evidently very delicate and extremely sensitive. The proper 

 function of the outer sac seems to be the protection of the inner 

 one, and on the final absorption of the vesicle a part of the outer 

 sac often drops off. 



The disease in question is generally known as the " dropsy " 

 or "blue swelling," and was, I believe, first so named in America 

 by Seth Green. In many cases, the part affected has a slight 

 bluish or bluish-grey tinge, from which it gets its name. There is 

 considerable reason for assuming that it is often caused by 

 using immature breeders, and it also occurs occasionally in 



