442 THE POPULAR SCIENCE MONTHLY. 



milt. The eggs thus become fecundated as they fall, and the develop- 

 ment of the young within the ova sticking to the bottom commences 

 at once. 



The first definite and conclusive evidence as to the manner in 

 which herring-spawn is attached and becomes developed that I know 

 of was obtained by Professor Allman and Dr. ]VIacBain in 1862,* 

 in the Firth of Forth. By dredging in localities in which spent her- 

 ring were observed on the 1st of March, Professor Allman brought 

 up spawn in abundance at a depth of fourteen to twenty-one fath- 

 oms. It was deposited on the surface of the stone, shingle, and 

 gravel, and on old shells and coarse shell-sand, and even on the shells 

 of small living crabs and other Crustacea, adhering tenaciously to 

 whatever it had fallen on. No spawn was found in any other part of 

 the Forth ; but it continued to be abundant on both the east and the 

 west sides of the Isle of May up to the 13th of March, at which time 

 the incubation of the ovum was found to be completed in a great 

 portion of the sj^awn, and the embryos had become free. On the 

 25th scarcely a trace of spawn could be detected, and nearly the 

 whole of the adult fish had left the Forth. 



Professor Allman draws attention to the fact that " the deposit of 

 spawn, as evidenced by the appearance of spent herrings, did not take 

 place till about sixty-five days after the appearance of the herring 

 in the Firth," and arrives at the conclusion that " the incubation prob- 

 ably continues during a period of between twenty-five to thirty days," 

 adding, however, that the estimate must, for the present, be regarded 

 as only approximative. It was on this and other evidence that we 

 based our conclusion that the eggs of the herring " are hatched in at 

 most from two to three weeks after deposition." 



"Within the last few years a clear light has been thrown upon this 

 question by the labors of the West Baltic Fishery Commission, to 

 which I have so often had occasion to refer. f It has been found that 

 artificial fecundation is easily practised, and that the young fish may 

 be kept in aquaria for as long as five months. Thus a great body of 

 accurate information, some of it of a very unexpected character, has 

 been obtained respecting the development of the eggs, and the early 

 condition of the young herring. 



It turns out that, as is the case with other fishes, the period of in- 

 cubation is closely dependent upon warmth. When the water has a 

 temperature of 53 Fahr., the eggs of the herring hatch in from six to 



* " Report of the Royal Commission on the Operation of the Acts relating to Trawling 

 for Herrings on the Coast of Scotland, 1863." 



f See the four valuable memoirs, KupfFer, " Ueber Laichen und Entwickelung des 

 Herings in der westliehen Ostsee" ; idem, " Die Entwickelung des Ileringsim Ei " ; Meyer, 

 " Beobachtungen iiber den Wachsthum des Ilcrings " ; Ileincke, " Die Varietaten des 

 Herings," which are contained in the Jahreshcricht der Commission in Kielfilr 18Y4-'76 

 1878. Widegrcn's essay " On the Herring," 18V1, translated from the Danish in U. S. 

 Commission Reports, 1873-'75, also contains important information. 



