38 



Part III. — Twenty-seventh Annual Report 



Immature. — In some cases the small reproductive organs had a soft 

 doughy or pasty condition ; the blood vessels were of large diameter. In 

 a fish 14 cm. in length, and in two larger fishes, the testis when teazed in 

 water showed a distinct network structure. This seemed at first to be 

 possibly a post-mortem change, but it is more probable that it is the first 

 stage of ripening. Small reproductive organs 2 to 3 mm. broad in imma- 

 ture herrings, 19 to 23 cm. in length, were, in some cases, flat but solid 

 with eggs ; others were soft and pasty, filled with ver} r small eggs. 



Many of the herrings included under the heading "W. Spr." are no 

 doubt ripening for the first time. Some have large eggs for compara- 

 tively small reproductive organs, e.g., two herrings 22 cm. in length had 

 ovaries 5 and 6 mm. broad, containing eggs '5 mm. in diameter. 



There is great difficulty in separating the immatures from the winter 

 spents. In August it is possible that the great amount of fat laid up in 

 the abdomen may crush the immature reproductive organ flat just as occurs 

 in the winter spents. I do not think it becomes quite so thin as in the 

 case of the spent. 



Winter Spent. — As most of the winter spents have begun to ripen, the 

 principal characters by which they may be detected have gone. They are 

 therefore included with herrings that are ripening for the first time, under 

 the denomination " Winter Spawners." 



There are still some herrings showing the spent condition. The repro- 

 ductive organs are small — in some cases flat and thin ; in others they have 

 become of a plump form, having commenced to ripen. It is a question if 

 the spents which are in the furthest back condition at present may not be 

 spring spents. In one fish the testis was a loose skin, and an open honey- 

 comb structure was present. This condition was accompanied by a great 

 quantity of fat. One fish that had eggs '35 mm. in diameter had in the 

 ovary some translucent nodules (? old eggs). 



A considerable number of herrings showing flat skin -like reproductive 

 organs, accompanied by great rolls of fat, was obtained at Laggan, Loch 

 Fyne. In one female a series of crystalline bodies were observed in the 

 oviduct ; they may have been old eggs. I have seen no indication of old 

 unspawned eggs being absorbed in the ovary. The testis showed the 

 honeycomb structure, in some cases filled up. 



Some of the herrings got at Campbeltown seemed to belong to the same 

 class of herrings as those captured there last month — viz., winter spents. 

 The eggs in some have commenced to store up yolk. Some ovaries were 

 supplied with their complements of eggs ; others were not. 



Some of the winter spents have no doubt grown since they spawned. In 

 an immature fish the ovary grows with a definite relation to the rest of the 

 body, but when a fish has spawned the ovary is disorganised, and is not 

 ready for some time to share in the growth which the fish acquires at once. 

 The ovary has to undergo a process of preparation, during which the new 

 crop of eggs is formed, and it meanwhile shrinks to a small size. It is not 

 ready to take advantage of the generous food supply of the spring and 

 early summer until after a certain period. There is no direct evidence to 

 show how long this preparation stage lasts ; it will not exceed six months. 

 Meanwhile the fish grows in length, and thick rolls of fat accumulate on 

 the gut and cceca. The reproductive organ is sometimes squeezed into a 

 flat skin between the gut and the swim-bladder. The flattened condition 

 of the reproductive organ may apparently also occur in an immature. We 

 have the condition where a large herring has a very small reproductive 

 organ. This fish, which one might be inclined to regard as immature, 

 might, however, be a spent. It is not possible to rely merely on the small 

 size of the ovary in diagnosing the class to which the herring belongs. 



The amount of fat present in the winter spent is an indication of how 

 long a time has elapsed since the fish spawned. Immediately after 



