XV.-THE THICK OR THIN FERTILIZATION OF EGGS. 



By G. F. Reisenbichler.* 



[From No. 20 of the " OesteD'eicMadh-ungarische Fischerei-Zeitiutg," Vienna, May 23, 1880.] 



It is well known that to this day practical pisciculturists are doubtful 

 whether the roe squeezed out of the female fish is to he put in a little 

 water, or whether it should be allowed to mix with the milt, and water 

 only be added after this process is finished. There are various reasons, 

 pro and con, interesting and important enough to form the subject of a 

 short article. 



The outer skin of the fish-egg is porous ; it consequently absorbs the 

 water from every direction and swells considerably. This process of 

 absorption, however, is finished in a very short time, and then the egg, 

 in a physical sense, is dead to its surroundings ; it exercises no power of 

 attraction on the water or on the sperm floating in it, and the latter has 

 therefore no occasion to approach the eggs from all sides and endeavor to 

 effect an entrance. On the other hand, it has been shown that the sperm- 

 atozoa when mingling with the water dies very soon, while it will keep 

 alive much longer when contained in the natural undiluted moisture of 

 the fish. These facts speak strongly in favor of mixing roe and milt 

 without previous addition of icatcr, as thereby the roe would waste its 

 power of absorption on the water and the sperm be made to die grad- 

 ually. The only objection which can be raised is that such a procedure 

 is not in accordance with the dictates of nature, which in such imita- 

 tions should be followed as closely as possible. This latter reason, how- 

 ever, is only seemingly correct and tenable, and at any rate is not appli- 

 cable to all cases. 



It is an open question whether the natural process is not an impregna- 

 tion of the egg if not entirely outside the water, at any rate with hut 

 a slight coating of the eggs with water, in which case the milt wouul 

 come in contact with the roe as if diluted, and the absorption of water 

 would only take place gradually. Some species of fish, moreover, have 

 some sort of copulation, approaching each other until their lpwer sides 

 almost touch, bringing roe and milt in such close contact with each other 

 that at least during the first moments a dilution by water can scarcely 

 be thought of. 



*Diclc odcr diinn Befruchten dcr Ekr, von G. F. Iieteenbichter.— [Translated by Her- 

 man Jacobson.] 



633 



