OBGANS OF GENERATION. 23 



,» 

 vertebral column and tlic " vasa deferentia," as their dncts are termed, uniting near 

 the termination of the urethra, while their contents or the seminal fluid, which is 

 white and of a thick, milky consistence, is popularly known as the soft roc or 

 milt. Under the microscope this substance is found to be composed of an infinite 

 number of microscopic organisms, termed spermatozoa or zoospcrms, which 

 consist of a small head and an elongated tail-like termination. These organisms 

 are exceedingly active dunng the period of their existence, the duratio'i 

 of which has been computed by different investigators at from two-and-a-half 

 to thirty minutes, but should they be jslaced in water their lives are rapidly 

 cut short, although a good deal depends upon temperature at which this takes 

 place. They are found to be surrounded by an alkaline fluid composed partly 

 of phosphates and partly of other constituents, and in it they will live for some 

 days, even after removal from the fish, provided no water be added, M. Vrasski 

 having kept them alive six days in a tightly-corked bottle. The reproductive 

 powers of this milt may be sufficiently matured in some Salmonoids at the 

 termination of their second year to be capable of fertilizing eggs although the 

 progeny may possibly be weak, sickly, or even imperfectly developed. 



In the female, the ovaries which are symmetrical organs are destitute of a 

 closed covering, while their internal surface is lined with stroma and transversely 

 plaited. Here the devclojjment of the eggs takes place, each of which is invested 

 by a fine membrane, and by it they hang suspended to the ovary, the length 

 of the pedicle decreasing- as the egg augments iu size. But as the ovaries are 

 destitute of oviducts it necessarily occurs that when the investing membrane 

 bursts the ovum falls into the abdominal cavity from whence it is extruded 

 through the abdominal pore. 



There is a considerable seasonable augmentation in the size of the procreative 

 organs in such of these fishes as are not sterile, while certain external secondary 

 sexual characters are also observable. In the male a knob appears at the upper 

 end of the extremity of the lower jaw, while the .skin on the surface of the head 

 and along the back becomes thick and spongy. At these periods also the colours 

 generally become more brilliant, and the fish takes less food, or even ceases 

 feeding. As eggs given by late breeding fishes cannot hatch out for some time 

 subsequently to those of the early breeders, much of the summer may 

 be consumed before the yelk-sacs of these alevins are absorbed, and as a conse- 

 quence the fry may be backward as winter sets in. Although the climate has 

 much to do with the period at which spawning* occurs, it would appear that 

 the organs of generation may be stimulated by certain kinds of foodf while, 

 should their diet be unduly reduced, such may cause seasonal sterilityj by 



* The term "spawn" is generally employed as denoting the eggs and milt that are 

 extruded from fishes, but in some looaUties it is likewise used when referring to the young 

 of these creatures prior to the absorption of the yelk-sac. While even in Acts of Parliament 

 it is not clear if this latter was not what was alluded to in the two following among many 

 other instances, more especially as the eggs of eels were then unknown. " None shall use any 

 Net, Device, or Engine whatsoever to destroy, kill, or take the spawn or fry of eels, pike, salmon, 

 oro£ any other fish," &c., 1 Eliz. cap. 17. " Every person who between the first day of March and 

 the last of May shall do any Act whereby the spawn of fish shall be destroyed shall forfeit the 

 instruments," &c., Stat. .3 Car. 2, cap. 9. 



t At Howietoun the clam Fecten, and mussel llytilus, having been scalded are used as food 

 for the purpose of stimulating the breeding fishes. 



{ At Howietoun it was observed in 1884, that the American Char {Sahno fontiimlls) suffered 

 a good deal from fungus, owing, it was beUeved, to their over-feeding. Consequently, in 18S5 

 their diet was reduced, and that with the best results as regards fungus ; but when the breeding 

 season came round it was found that large numbers were sterile. That this is solely a question 

 of food a most interesting instance in pond No. 5 may be quoted. Here the hybrids were kept 

 and fully fed, and one female foniinnlif: was placed along with them. She attained to a large 

 size, and in November, 188.5, was found to be full of eggs. In August, 1886, my attention was 

 directed to two ponds at Cowley, near Cheltenham, which, after having been drained, mudded, and 

 ))uddled with clay, were stocked in December, 1884, and January, 188-5, with yearling Lochleven 

 trout, received from Mr. Andrews of Guildford. Due to causes which will subsequently bo fully 

 referred to, those in the upper pond did not exceed seven inches in length, and were sterile, those 

 in the lower pond were much better nourished, averaging about eleven inches in length, and had 

 the generative organs well developed. 



