1206 



SCANDINAVIAN FISIIKS. 



mm. These eggs ai"e enveloped in a firm ineiiihrane 

 and yellowish in colour; the greater part of their eon- 

 tents consists of yolk. In its hindmost ])art the said 

 ovarian mesentery (mesorarhim) jtresents a totally dif- 

 ferent appearance; no eggs are visil)le here, and the 

 mesentery assumes a still more lobate, tuberculate or 

 granular form. On microscopical examination no eggs 

 are found here, but only vesicles or capsules, contain- 

 ing a great number of large cells, many of which are 

 in process of division. I. T. Cunningham" was the 

 first to express the opinion, based on his investigations, 

 that tins hindmost part of the mesentery is a mesor- 

 chium and contains the male organ. Nay, he even 

 considered that he had here found spermatozoa at dif- 

 ferent stages of development. Fridtjof Nansen' fol- 

 lowed up these researches and adopted the theory of 

 hermaphroditism, adding that he had observed that, in 

 young individuals which liad not yet attained a length 

 of 320 — 330 mm., the male organ was, as a rule, the 

 more developed and contained almost ri]5e s))ermatozoa, 

 whereas the female organ ■was more or less undeve- 

 loped. Larger (older) individuals he found, on the 

 other hand, to contain more developed female organs 

 and also large eggs, wliile the male organ was more 

 rudimentary. Hence he concluded that in the j'ounger 

 stages of its development Mi/xine is masculine (prot- 

 andric), but afterwards in the older stages feminine. 

 But there besides occur, according to Nansen, indivi- 

 duals that are males alone. The same investigator also 

 gives figures of spermatozoa he had observed in Mjixine, 

 and asserts that those described by Cunningham are 

 not of a true nature. The latter writer has subsequently 

 given a new description of the spermatozoa observed 

 by him, and insisted ujjon his priority \vith respect to 

 the theory of hermaphroditism. As I mj'self too, during 

 a series of years (since 1877), have made repeated in- 

 vestigations into the structure of Myxine and its mys- 

 terious development, 1 will state that, so far as I can 

 find, no distinctly developed male individual thereof 

 lias hitherto been observed \vith certaint)-, and that 

 there is much to be said for the Cunningham-Nansen 

 theory of its hermaphroditism. Considering that I have 

 raacroscopically examined a great number of Hag-fishes 

 and have microscopically prosecuted these investigations 

 in many instances that seemed especially i-emarkable as 



regards the point in (luestion, and this at every season 

 of the year, it may a])pear strange that I have never suc- 

 ceeded in iinding within the cell-filled vesicles of the so- 

 called mesorchium fully developed spermatozoa, but only 

 lower and some^vhat dubious stages thereof. Yet from 

 preparations kindly sent me by Nansen it would seem 

 that the structures found by him presented in a high 

 degree the appeai'ance of spermatozoa. Phenomena of 

 movement, however, have not yet been observed in 

 them, and even their development is not fully known". 

 As for the season of impregnation and oviposition, 

 these do not ajjjjear to be restricted to any fixed time 

 of year. All the investigators who have made any 

 minute researches into this question are a]j])arentlj' 

 agreed that ripening eggs are met witli in these crea- 

 tures all the year round, but that at the same time in 

 other individuals ova may be found at the most different 

 stages, from (piite small, colourless globules, hardly 

 distinguishable to the naked eye, to the opaque, yellow- 

 ish eggs 10 — 12 mm. long, of an elongated oval form, 

 pointed at the ends, enveloped in a horny shell, and 

 filled for the greater part by a large j-olk. Of such 

 ripening, but not j'et fully developed eggs a rmmber 

 of 10 — 15, up to 26, are as a rule found in the same 

 individual, all then exhibiting the same size and ap- 

 pearance. These ova, however, as mentioned above^ 

 are not quite ripe for deposition. There are a few in- 

 stances in which specimens have been secured of fully 

 developed eggs. In 1859 Allen Thomson figured and 

 described in Todd's Cyclopedia of Anatomy and Phy- 

 siology ova of Myxlnc that measured about 25 ram. in 

 length, had an oval form, and were furnished with a 

 firm, horny shell and at each end with a number of 

 horny threads, each having hooks (barbs) at the end. 

 Some years afterwards J. Steenstrup (Oversigt af d. 

 K. Danske Vidensk. Selsk. Forhandl. f. 1863) described ■ 

 and figured eggs of similar appearance that had been 

 found in a Glutinous Hag. A. W. Malm (Goteb.. Bohusl. 

 Fauna) also secured ripe eggs 19 mm. long that were 

 met with in the stomach of a (^od (thus ])resumably 

 devoured after their deposition) ; a couple of these were 

 described in 1875 by W. Muller in the "Jenaische 

 Zeitschrift f. Naturwissenschaft". Furthermore I. T. 

 Cunningham has described in the Quart. Journ. of Micr. 

 Sc, N. S., V. 27, 1887 an egg preserved in the Edin- 



" I. T. CuNiNiNGHAM, Quart. Jipurniil of Miirosc. Science, N. S., V. 27, 1887. 



'' Fhidtjof Nansen, Bcrgens Museums Aarsberetuing f. 1887 (ed. 1888). 



' See further G. Retzius, Biolog. Foreningens Forhandl., Bd 2, No. 8, 1889—90. 



