96 



Appendices to Fourth Annual Report 



separated from the ovarian septa and on their way to the exterior, while there 

 were also present, and scattered thickly throughout the ovary, immense 

 numbers of small ova which were certainly not likely to be shed for many 

 weeks, probably not for some months. I am not referringhere to the evidence 

 of microscopic examination, but to ova which were sufficiently developed to 

 be readily seen by the naked eye. There is nothing extraordinary in finding 

 ova of such different stages of development as this where the animal de- 

 posits its eggs gradually and where ova are found in various intermediate 

 conditions, but all present at one time; but in the case of the herring we have 

 a fish spawning in a very limited period of time, and presumably only once 

 a year, with ova which will be ripe about twelve months later, and yet are 

 already fairly well developed before it has completed its present spawning. 

 The circumstance that such large numbers of herring with ova only quarter 

 or half ripe are caught during the principal spawning seasons points to the 

 conclusion that these fish will spawn during the following month or two 

 at most. Between what I have called quarter-ripe and the condition 

 which I have been describing in the spent fish there is not much differ- 

 ence, so we must conclude that if these herrings are not to spawn again for 

 a year, the ova develops very little during about nine months of that time. 

 These observations were made on summer fish, but when examining the 

 winter specimens my attention had not been attracted by this condition, 

 and very probably it had been overlooked. 



The size of the egg found in the ripe fish is of importance especially 

 with regard to the question of variety among the herrings. Kupffer has 

 found the ripe eggs of more than one size in the Baltic herrings, from "92 

 to 1 mm. in diameter, while Boeck puts that of the North Sea herring at 

 1'5 mm. I have measured the eggs of several of the Scottish East Coast 

 herrings and have found them vary slightly in size in the same fish, from 

 1*27 mm. to 1*42 mm. diameter; ova of these sizes were found in herrings 

 of 230 and 240 mm. length (about 265 and 275 mm. total length). The 

 commonest size was 1*27 diameter, but the larger and intermediate sizes 

 were found together in the same spawning fish. In fish of about 215 mm. 

 length the diameter of the ripe egg varied from '94 mm. to 1 mm. 

 In all cases the eggs were fully ripe, being taken from spawning 

 fish, and were measured before the inception of water. None of the 

 eggs were found so large as those mentioned by Boeck, and were rather 

 larger than Kupffer's, but the point of importance here is the fact that 

 the ova of the herring showed an increase in their average size corre- 

 sponding to increase in size of the fish.* This month (February) herring 

 have reached me from Ardrishaig which measure only 165 to 170 mm. 

 long (190 to 200 mm. total length), being samples of the ordinary takes 

 with seine net in upper Loch Fyne.f Some of these small herrings had 

 fully ripe roe or milt, others half ripe, and others of the same size were in 



usual number seems to lie between 20,000 and 35,000. Prof. Huxley {Nature, 

 April, 1881) considers 30,000 eggs an over estimate due to forgetfulness that the 

 ovary consists of an extensive vascular network, and that a vast number of eggs 

 remain immature and unshed. In the herring just commencing to spawn, however, 

 these latter are so minute and little developed as scarcely to affect the question. But 

 my calculations were made with due allowance for both these objections. 



* The average of many measurements of spermatozoa shows that they also were 

 larger than those of the Baltic herring, being "0033 mm. in head length, and having a 

 filament of "066 mm. Kvipffer's measurements only give '0025 mm. for head length, 

 the tail being '062 to -075 mm. 



t Ljungman states having received herrings of only 100 mm. in length (the size 

 of a sprat), full and ready to spawn. Of about 3000 young herrings which I have 

 examined during the last year or two, the smallest in which I have found ripe or 

 nearly mature ova measured 185 mm. total length (7^ inches), none less than this 

 length showing the slightest approach towards this condition. 



