74 Bashford Dean Memorial Volume 



hundreds of specimens, the Schreiners decided that all Myxines are to be placed in three 

 groups, vi?., male, female and sterile individuals. 



In the males the testis is well developed, occupying a greater or lesser portion of the 

 posterior end of the sex organ, while an ovary is either not at all developed, or if present 

 is more or less rudimentary and always shows signs of degeneration. Ovaries present in 

 ripe males are always abnormal and not well developed. As a rule, in the males the 

 anterior portion of the sex organ consists of a rudimentary ovary which contains quite 

 small eggs. The number of pure males, i.e., individuals with only a testis in the sex 

 organ, was found to be insignificant. All transition stages of males were found between 

 those in which the testis occupied only the posterior 0.7 cm. of the sex band, and those in 

 which the testis extended the entire length of the band. 



In the females the anterior portion of the sex organ always consists of an ovary with 

 normal eggs, while the posterior end is either entirely lacking in sex elements, or consists 

 of testicular tissue which is slightly developed and shows signs of degeneration or other 

 abnormalities. As a rule, the females have nothing in the posterior part of the meso- 

 varium; in many young females, however, and in some of the older ones, the posterior 

 part of the mesovarium is not entirely empty, but contains an abnormal testis which never 

 becomes functional. The testis present in specimens having well developed ovaries in the 

 anterior portion of the sex band is always abnormal and non-functional, whether in an old 

 (33 cm. long) female or in a young one (25.5 cm. long), and it shows no indications of ever 

 having produced spermat02,oa in either young or old females. The Schreiners found all 

 transition stages of females from those in which the ovary contained a single small egg to 

 those in which the entire ovary was filled with eggs up to the posterior 7 mm. of the mes- 

 ovarium. 



The sterile individuals are those in which the posterior end of the sex organ consists 

 of an abnormal, degenerate testis, and the anterior portion is an abnormal, degenerate 

 ovary. These individuals never attain sexual maturity, either as males or females, i.e., 

 they are sterile throughout the entire extent of their lives. They fall into two main groups : 



(1) the completely sterile, in which there is no trace of either testicular tissue or of eggs; 



(2) those whose sex organs consist of both testis and ovaries both of which are abnormal 

 and attacked by degeneration processes. Among 1690 eels examined, 13.1 per cent were 

 sterile individuals. 



Unlike Cunningham and Nansen, the Schreiners observed no relation between 

 body length and sex. They found males in great numbers 25 cm. long with almost ripe 

 spermatozoa, and males 29-30 cm. long which were not ripe and which, according to the 

 structure of the testis, apparently had not produced sperm at any earlier time. They 

 found females 26-27 cm. long which had large empty egg cases (corpora lutea) hanging to 

 the ovary, clear proof that they had deposited eggs, and they also found good females over 

 31 cm. long which had never laid eggs. They found large ripe males (30 cm. long), large 

 females (37 cm. long) and large sterile individuals. As a rule, however, the females were 



