Genital System of the Myxinoidea 73 



Upon the whole, it must be admitted that there is a strange irregularity in the occur' 

 rence and extension of the male and female organs m Myxine. Myxine seems to me to be an 

 animal which, in sexual respects, is just at present in a transition-stage; from what and to 

 what, it is however not easy to say. It seems still to be seeking, without yet reaching, that 

 mode of reproduction which is most profitable for it in the struggle for existence. 



A few years later Cunningham (1891) published the results of further investigations 

 upon spermatogenesis in Myxine. For the purpose of making this study he spent several 

 weeks at Alvarstrommen, Norway, and was supplied with eels caught in traps. He wrote 

 as follows (p. 170): 



In the morning the specimens caught were brought to me. The number varied from 

 about fifty to ninety, and out of these I found rarely more than two or three in the required 

 condition. . . . All the testicular elements which I am about to describe were obtained 

 from hermaphrodite specimens, individuals in which the whole of the generative organ is male 

 being exceedingly rare. The numerous specimens of the animal which I examined were from 

 25 to 42 cm. in length. In all the larger specimens ova in various stages of growth were 

 found, but no testicular tissues, the posterior 5-7 cm. of the generative organ being sterile. 

 In all the smaller specimens only very young ova were found in the anterior part of the gen- 

 erative organ; these young ova are usually round, not ellipsoidal as they become when more 

 developed, and only about 2 mm. in diameter. In such specimens the posterior 5 to 7 cm. of 

 the organ is male, consisting of testicular tissue in various stages of development. The limit of 

 size, between the functionally male hermaphrodites and the larger female specimens in 

 which the testis has atrophied, is, of course, not absolutely constant. I found no testicular 

 tissue in specimens more than 35 cm. (about 14 inches) in length, and it was sometimes absent 

 in specimens smaller than this. On the other hand, I rarely found traces of actual spermato- 

 genesis in specimens less than 30 cm. long. Specimens containing mature testicular tissue are 

 thus usually between 30 and 35 cm. in length, and aftpr a Uttle practice I was able, by simply 

 comparing the sizes, to select from a large batch of specimens all the individuals in which 

 mature testes were likely to occur. 



In this paper Cunningham illustrated "perfect ripe spermatozoa" which he had 

 observed "in motion" under the microscope, but he found that only a small number of the 

 capsules contained ripe spermatozioa. This was the last publication by Cunningham in 

 regard to this subject. 



Between 1904 and 1908, A. and K. E. Schreiner published several papers presenting 

 the results of extensive investigations made upon Myxine glutinosa at the Biological 

 Station of the University of Christiania, now Oslo, at Drobak, Norway, with particular 

 reference to the development of the male sex cells. From their references it is evident 

 that these authors were influenced by Professor Dean, who visited Drobak during that 

 time. They stated that the hypothesis of protandric hermaphroditism for the condition 

 in Myxine as advanced by Cunningham and Nansen was at that time generally accepted 

 and had been printed in all modern text-books, and that only Bashford Dean (1899) ex- 

 pressed strong doubts as to the truth of this hypothesis. After two years' work, in which 

 time they examined very thoroughly, both macroscopically and microscopically, many 



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