200 Part III. — Thirteenth Annual Report 



* lated organs are filled with grains which are confined to compartments 



1 separated by fibrous membrane. I may say that this description is in 

 1 general terms correct, but would point out that these compartments are 

 1 more or less convoluted, long, and tubular, and therefore present the 

 ' character of true spermatic tubuli. I find that the granules alluded to by 

 4 Syrski are really the heads of what in future will become spermatozoa, for 

 4 they are globular and nearly uniform in size. Another important fact I 

 4 would point out, viz., that the Syrskian lobules of the testicle of the male 

 1 eel correspond almost exactly with the muscular and skeletal segments of 

 4 the animal, a trait which is not discoverable in the female organs, and one 

 ' which illustrates a singular fact in morphology, viz., that metamerism 

 ' may show itself in the glandular part of the reproductive organ of one sex, 

 1 and not manifest itself in the structure of the generative apparatus of the 



* other.' 



Robin gives in La Journal de VAnatomie, etc., 1881, a detailed 

 and very clear description of the minute structure of the testis of the eel : 

 — 1 The lobulated testis is traversed throughout its length by seminiferous, 

 4 or testicular tubes, or cylinders — which are flexuous, twisted, and termi- 



* nated csecally at both ends, at least out of the breeding season : that is to 

 ' say, falling into the type of canaliculate testis, such as that of the carp. 

 4 Out of the period of reproduction, the seminiferous tubes are O^OS-O^OQ 

 4 mm. in thickness, cylindrical, twisted in various directions, and ramifying 

 ' once or twice. Some of them anastomose with their nearest neighbours. 



* Their extremities are rounded and closed, with or without a slight 

 4 dilatation. One of the extremities is usually situated close to the surface 

 4 of the lobe, which is covered with a delicate peritoneal tunic. None of 

 1 the tubes is particularly directed towards the deferent canal, and none 

 4 opens into the latter. The flexuosities of the tubes, their volume, and 

 ' their structure give to the tissues of the organ the characteristic arrange- 

 1 ment and appearance usually observed in the testicular tissue of the 

 4 higher vertebrata. It is only by an enormous dilatation at the breeding- 

 4 season that we can imagine these canaliculi at the state of seminal 

 4 capsules. These tubes are imbedded in a dense web of cellular tissue 



1 without adipose vesicles, and of a thickness, between the tubes, of about 

 4 half that of the latter. The ramifications of the blood-vessels coming 

 ' from the bases of the lobes run along with the tubes, and form around 

 ' each of their rounded extremities, at the surface of the organ, a circular 

 ' mesh 0 08 mm. in breadth ; these meshes together form an abundant net 

 1 work. One might be led, by the examination of the entire lobe before 

 4 making sections, to suppose that these meshes enclose so many closed 

 ' vesicles, or seminal capsules, whereas we really have in each mesh simply 

 ■ the extremity of a seminiparous canaliculus. This description might be 

 ' taken as giving the general type of the structural disposition of the 

 ' testicle of osseous fishes, apart from the period of ripeness. It is, indeed, 

 4 in this case, a reduced disposition to a single and small lobe, in place of 

 4 the long continuity existing in the unilobed testicles of the greater 

 ' number of species, but it is none the less characteristic. The same 

 4 remark applies to the following facts concerning the special structure of 

 4 the individual tube. In a series of preparations of M. Herrman, I have 

 4 been able to show that these tubes are composed of a peculiar thin wall, 

 4 which is hyaline and homogeneous, plaiting or folding easily, and adher- 

 4 ing strongly to the tissue surrounding it. The inner surface of the tube 

 4 is uniformly lined with a single row of regular prismatic epithelial cells 

 4 with polygonal bases, which separate easily from the thin wall of the tube. 

 4 These cells are attenuated at their inner extremities. The straight canal, 

 4 of which these cells form the boundary, is often closed through the con- 

 4 tiguity of the inner extremities of the latter. The contents of the cells 



