1884. J Artificial Fertilisation of Herring Ova. 



461 



to expel the eggs by the genital aperture. The eggs as they escaped 

 were received on a plate of glass, and then spread over the surface of 

 the glass by means of a feather. Milt was then added directly from 

 the male, and spread in the same way. After immersing the glass 

 plate several times iu water it was introduced into the hatching or 

 carrying box. By this method the eggs were often distributed in a 

 very irregular manner over the surface of the glass, and they were 

 liable to be over-milted. The eggs which first escaped collected in a 

 mass around the genital aperture, and were apt, unless the herring 

 was retained in a perfectly natural position, to run along the side and 

 get contaminated with loose scales, &c, and when they fell on the 

 surface of the glass, or were conveyed to it by the finger or the end 

 of a quill, they formed irregular lumps into which the sperms could 

 not easily penetrate. 



I found, after many experiments at Ballantrae, that the best 

 results were obtained when both the male and female were held under 

 water while the milt and roe escaped, i.e., when the natural process of 

 spawning (although not known at the time the experiments were 

 made) is followed. 



An ordinary wooden tub was obtained and filled with sea- water. 

 Into this a small quantity of milt was expressed, the male being held 

 completely under water while the milt escaped. A glass plate was 

 then held about 4 inches beneath the surface of the water and the 

 female herring about 1 inch beneath the surface, and then under 

 gentle pressure the eggs readily escaped in the characteristic narrow 

 beaded ribbon, and by moving the fish over the surface of the glass 

 either a close or an open network could be formed. At first, where 

 one loop crossed another, the eggs were two or more layers thick, but 

 either owing to the weight of the eggs or the gentle currents set up 

 in the water, before a few minutes had elapsed the eggs usually 

 formed a single and almost continuous layer, the network arrange- 

 ment having disappeared. The plate was then allowed to rest for two 

 or three minutes at the bottom of the tub and a few short ribbons of 

 milt were again introduced. After moving the plate once or twice 

 across the top of the tub in order to wash off any scales that were 

 adhering, it was placed either in a hatching or in a carrying box. 



]\Iany thousands of ova treated in this way on the 8th March contain 

 extremely active embryos, which are expected to hatch on the 22nd 

 or 23rd of March. 



