442 THE EEL FAMILY. 



ovaries. These have been found to contain great numbers of 

 very minute eggs. In the ripe eel examined by Rathke the 

 largest eggs only measured '1 mm. in diameter. This is one 

 of the two ripe eels which have been recorded, and it is 

 remarkable that the eggs in this case were much smaller 

 than those subsequently found in unripe ovaries. The 

 largest eggs described by observers have been - 27 mm. in 

 diameter. Syrski noticed that a more advanced state of de- 

 velopment of the egg was found in those eels in which the 

 fissura recto-vesicalis and the genital aperture were open, than 

 in those in which they were closed. 



As regards the male organ there has been some little doubt 

 and uncertainty. What is undoubtedly the testis of the eel was 

 first described by Syrski in 1874, under the name of ' lobe- 

 organ.' No observer has, so far, found ripe spermatozoa in 

 the lobe-organ of Syrski, but the histological examination of 

 the lobes, made by several zoologists, have shown that this 

 organ exhibits a minute structure, similar to that found in the 

 immature testis of other fishes. The discovery of spermatozoa, 

 also, in the homologous organ of the conger, by Dr Hermes, 

 affords conclusive proof of the testicular nature of the lobe- 

 organ. The testis occupies in the body of the male a position 

 corresponding exactly to that of the ovary in the female. 



Such then are the organs of generation in the eel ; it will 

 be seen that there is no feature in them in comparison with 

 those of other fishes to lead us to suppose that there are any 

 exceptional anomalies in the deposition of spawn and its 

 connected phenomena. 



Grassi 1 , to whose work we refer again below, has been 

 enabled to obtain from the straits of Messina male eels with 

 ripe spermatozoa. He found that all the eels so obtained were 

 ' silver,' and confirmed the suggestion of Petersen that the silver 

 colour was a 'breeding dress.' He further showed that the 

 pectoral fins become at this stage an intense black, and in some 

 the anterior margin of the gill-cleft is of the same hue, whilst 

 there is a marked increase in the size of the eyes. 



Prior to maturation of the sexual products the great 

 1 Q. J. Mic. Sc. Nov. 1890. 



