lviii BREEDING. 



the stroma does not extend to the hind portion of these sacs, for this locality 

 serves as a sort of uterus, and is furnished with a large albuminous secretion, 

 while internal incubation is going on. The products of the reproductive 

 ' organs may be set free in the peritoneal cavity, finding their exit at the 

 abdominal pore or pores : or these products may be taken up by the open 

 mouths of the fallopian tubes, or distinct tubes conduct them all the way to 

 their outlet. 



The various modifications of the generative organs in true fishes are a 

 simple testis or ovary, but no excretory duct ; a partial: oviduct united to the 

 ureter, but not continuous with the ovary; or a testis having a long and 

 complex duct distinct from the ureter. Among teleostean fishes breeding 

 occurs in one of the following ways: — 1. The eggs are hatched within the 

 female organs, as seen in the oviparous blenny, Zoarces viviparus (vol. i, 

 p. 211). 2. As in the majority of these fishes, the eggs having been 

 excluded, are subsequently fertilized by the male, the milt or spermatozoa of 

 the latter being brought into contact in the water with the ova or eggs of 

 the female, when this microscopic body (the spermatozoon) obtains access by 

 a minute orifice, termed the micropyle, into the interior of the ovum. In 

 short, during the breeding of osseous fishes the generative organs perform 

 the following functions: — " Semination/' "ovulation/' " fecundation/', and 

 " exclusion," to which in some forms is added that of " foetation." 



Simple- as this process would seem to be, there are many interesting 

 questions about it which are still unsolved and require attention.. If all 

 fishes' eggs were of one size, -the micropyle and spermatozoids identical in 

 all forms, the specific gravity of all ova without variation, and all kinds of fish 

 propagated their species at the same, period and took the same time, in the 

 incubating process, we should soon arrive at a state of inextricable 

 confusion. There might be hybrids between salmon ' and minnows, perches 

 and bullheads, sticklebacks and carps : and were these hybrids to prove 

 fertile, in a comparatively very short space of time all land-marks would be 

 obliterated; families, genera, and species would be things of the past. And 

 if this did occur, the result could be readily foretold; now small forms obtain 

 sustenance in little as well as in large pieces of water ; but were these small 

 forms to merge into the larger, our brooks, our lesser streams and ponds 

 would no longer be stocked with fish ; for the size of the stream and the 

 amount of the food would be insufficient to maintain them in health, even 

 were it sufficient to sustain life. And could we hope for a hardy race from 

 young raised under such conditions? Or even were our fishes entirely 

 restricted to our larger rivers, what would occur ? Predaceous forms of 

 destroyers, perhaps man himself, would soon diminish, and possibly 

 annihilate them. Irrespective of which, deterioration in the size of parent 

 fish may be equivalent to diminution in the size of the offspring, such being 



