TENCH. 25 



comparative size of tlieir ventral fins; -which in the male are 

 far the largest, with a stout, thick, crooked, and transversely 

 striated first ray. The bones also to which these fins are attached 

 are large, thick, and extended even to the gill openings. 



Willoughby remarks, from Schenckfeld, that the Tench 

 spawns at the time when wheat is in blossom. The spawn is 

 shed at no great depth in the water, and the development of 

 the grains is rapid, as they were traced by M. Rusconi in 

 Muller's "Archives," for 1836; who observes that soon after 

 the application of the milt the ovum loses its spherical form, and 

 swells out into the form of a pear, and at the point where the 

 swelling begins it is surrounded with a cluster of microscopic 

 globules, which before were spread all over its surface. In 

 half an hour the pear-shaped excrescence is divided into four 

 globules, which in another quarter of an hour are subdivided 

 into eight, and after a similar period into thirty-two, which still 

 remain clustered together on the top of the egg. In another 

 half hour more globules appear, which become less in size as 

 they increase in numbers, and at length from their minuteness 

 that part of the egg to which they are attached becomes almost 

 as smooth as before they made their appearance. The embryo 

 fish is now seen in the form of a whitish transparent speck, 

 which is the rudiment of the backbone. The organization of 

 the skin then proceeds, and the embryo as it is coiled round 

 the yolk increases in length until the head becomes perceptible, 

 In forty hours from the first this embryo Tench gives signs of 

 motion, and in further twelve hours it has freed itself from the 

 skin of the egg; at which time the fish is two lines in length, 

 and the blood is of its natural colour. For some hours after 

 leaving the egg the young appear inert; lying on their sides 

 and unable to swim; but when the swimming bladder becomes 

 developed they assume their proper position and activity. The 

 intestines are not fully developed until seven days from leaving 

 the egg; and then they begin to feed voraciously, but only on 

 animal substances. 



The narrative here given may be considered as generally 

 applicable to fishes of this family, and in its outline to fishes 

 in general; since the variation is rather connected with the 

 quickness of the development than the mere order of the pro- 

 ceeding; and in regard to quickness it is much influenced by 

 VOL. IV, E 



