of the Fishery Board for Scotland. 



201 



' are finely granular, enclosing a relatively large hyaline nucleus without 

 4 granules. In the nucleus there is a bright yellow nucleolus. These cells 

 1 break off by dissociation, and give to the liquid of the preparation an 

 ' opaline or milky appearance. 



* A deferent canal, about 1 mm. in diameter, adhering to the internal 

 ' or dorsal thin wall of each lobe, runs along the whole extent of each 

 1 testicle. The wall of this sperm duct is about J mm. in thickness. It is 

 1 composed of two layers, an internal layer of longitudinal fibres, and an 

 4 external layer of circular fibres. The bundles of fibres of both layers 

 4 freely intermingle with those of the envelope of the male organ at the 

 ' base of the lobe, and a little also on its external surface. These layers 

 4 are composed of cellular tissue, mixed with smooth muscular fibres. 

 4 A single row of small polyhedric epithelial cells lines the internal surface 

 1 of the deferent canal. Adhering to the internal edge of the thin testicular 

 1 lobes, the vas deferens is thus lodged in the peritoneal fold connecting 

 4 the testicle to the swim bladder, and to the superior parts of the abdominal 

 1 wall. 



1 It is important to institute a comparison with the male organs of 

 4 other fishes. A thin hyaline wall constitutes essentially the seminiferous 

 4 tubes of other fishes in general. An epithelium of small polyhedric cells 

 4 distinct from the male ovules, at least in approaching the time of milting, 

 4 lines the tubes. The male ovules at this period attain a diameter of 0*06 

 4 mm. or more, and fill up and distend the tubes ; they become regularly 

 4 polyhedric by mutual pressure, and are full first of spermatoblasts and 

 4 then of spermatozoids. The tubes, now whitish in colour, are perceptible 

 4 to the naked eye. The epithelium of the tubes always remains distinct 

 4 from the male ovules in the different stages of spermatogenesis. The 

 4 testicular tissue in the ripe condition is friable, and allows the direction 

 4 of the tubes, which are accompanied by capillaries, to be seen by the eye 

 4 or lens at the surface of the torn tissue. The csecal termination of these 

 4 tubes, which may or may not end in slight swellings, with or without 

 4 capillary meshes round them as in the eel, give to the surface of the 

 4 testis a dotted whitish appearance. These testicular tubes are reticulated, 

 4 that is to say, they ramify and anastomose, as in other vertebrates in 

 4 general, having interposed between them a delicate and fragile woof of 

 4 cellular tissue without adipose vesicles, but accompanied by numerous 

 4 capillaries, as indicated above. At their opposite or internal extremities, 

 4 the tubes become narrower, and open either into a central common 

 4 cavity connected with the deferent canal, or directly into the deferent 

 4 canal. In a certain number of species their internal extremities are 

 4 closed, and open either into the sperm duct, or into the peritoneal cavity, 

 4 at the time of milting only.' 



Certain stages in the development of the testis are described by Syrski, 

 who says : — 4 As regards the development of the spermatic organ, I have 

 4 observed that the lobes of these organs in young eels measuring not more 

 4 than 200-300 mm. (8-1 2 inches), are not yet very distinct, forming two 

 4 thin ribbons, differing but little from the ovaries of the female in their 

 4 average size. In eels measuring about 400 mm. (16 inches), the testicles 

 4 can easily be distinguished from the ovaries. The former, much straighter 

 4 and with tissue much more solid, are provided with a more developed net- 

 1 work of vessels ; their lobes are very distinct and the deferent canals are 

 4 usually open, while the ovaries present the appearance of two continuous 

 4 ribbons, have a more delicate tissue and an almost glassy appearance, 

 4 and contain eggs with the germinative vesicles. The deferent canal and 

 4 the genital orifice are closed in young eels of the male sex, and open 

 4 simultaneously with the development of the lobes. In the male eels 

 4 examined by me from March to October, I have found individuals of 



