372 ZOOLOGY. 



for a long time involved in obscurity, but many data have been accu- 

 mulated within the last few j^ears, and now we have the elements for a 

 pretty satisfactory determination of the sexes. The ova and m ilt have 

 been found by several investigators, and the last statement is that the 

 individuals of the two sexes may be distinguished by external character- 

 istics. In the female eel the snout is comjiaratively narrow, and a very 

 considerable size is sometimes attained. In the male eel the snout is 

 notably broader, and the length attained rarely exceeds 19 or 20 inches. 

 The eggs of eels when mature are only about one-tenth of a millimeter 

 in diameter, and there are several millions in the ovary of a moderate- 

 sized individual. It is now well determined that they go to the sea, and 

 there the sexual organs are developed, and in comparatively deep water 

 the ova are deposited and fecundated. The young in due time ascend the 

 rivers. The eel is thus an example of a catadromous fish — that is, one 

 descending from the fresh water into the sea to breed ; and thus contrasts 

 with the salmon, shad, &c., which are anadromous — that is, ascending 

 from the sea into fresh water to breed. 



PLEURONECTIDS WITHOUT PECTORALS. 



As is well known, some of the Soleids are more or less deficient in 

 pectoral fins, and one genus has been named on account of the total 

 absence of these members Achirns. Until lately, however, no Pleuro- 

 nectids, in the restricted sense of the term, were known to be destitute 

 of the fins. There nevertheless seem to be quite a number of forms be- 

 longing to the family inhabiting waters of considerable depth in which 

 the pectorals are reduced, or may be even almost entirely wanting. 

 Several types show gradations in that the fins in question are less de- 

 veloped and that of the blind side disproportionately small, but in 

 Monolene sessilicauda of Goode* the pectoral fin on the blind side is 

 "totally absent," and in a new type called Lepidopsetta maculata bj'" 

 Gunther, discovered by the Challenger expedition near the Antarctic 

 Ocean, "off Prince Edward's Island," we have the "pectoral entirelj-^ 

 absent on the blind side, and represented by a small rudiment only on 

 the colored."! 



It may be here added that Lepidopsetta of Gunther is entirely dif- 

 ferent from Lepidopsetta of Gill, and therefore should have a diiferent 

 name. Mancopsetta may be substituted and refers to the defective 

 l)rovision with fins. 



* Goode (G. Brown). Descriptions of seven new species of fishes from deep soundings 

 on the southern New England coast, with diagnoses of two undescribed genera of 

 Flounders, and a new genus related to Merlucius. Proc. U. S. Nat. Mus., vol. iii., 

 pp. 337-350 (338). 



tGiinther (Albert). Report on the scientific lesults of the voyage of H. M. S. Chal- 

 lenger during the years 1873-'7G. Zoology, vol. i, part vi. Report on the Shore 

 Fishes. London, 1880. (p. 18.) 



