324 



Reproductive Organs. 

 I have so far not paid much attention to the reproductive organs, 

 but I can confirm one very important point in the recent work of 

 Schreiner ^), and had in fact independently arrived at this result 

 before Schreiner's work appeared. There is no protandric herma- 

 phroditism in Myxine, as indeed was to be inferred from recent work 

 on Bdellostoma. Without accepting or rejecting the existence of 

 Schreiner's sterile forms, we may state generally that every adult 

 Myxine is hermaphrodite, but either predominantly male or female, 

 the posterior extremity of the gonad representing the testis and the 

 remainder or greater part the ovary. Hence every adult Myxine has 

 either a mature testis and a rudimentary ovary, or a mature ovary and 

 a rudimentary testis. 



Teeth. 



The ventral teeth of Myxine form two comb-like structures on 

 each side. Each cusp of each series is situated over an epidermal 

 papilla, and these papillae, like the horny cusps also, are joinedup 

 at their bases. Nevertheless a longitudinal section of the teeth of an 

 adult animal shows that the basal horn connecting the cusps, and the 

 basal tissue connecting the epidermal papillae, is in both cases of a 

 different nature to that of the cusps and papillae themselves. There 

 is only one exception, which is that the first two cusps of each row 

 are not separable in this way. Each cusp therefore respresents an 

 independent tooth except the first two of each row which represent 

 a single bifurcated tooth. 



The dorsal transient larval teeth of Beard ^j are, without question, 

 simply the normal adult ventral teeth which have become accidentally 

 displaced to a dorsal position. 



Thyroid. 

 The thyroid of myxinoids has not hitherto been described. It is 

 a diffuse thyroid, consisting of a number of closed independent alveoli 

 scattered along the whole course of the ventral aorta. These alveoli 

 may be small or large, simple or sacculated, and they contain usually a 

 reticular and occasionally the characteristic waxy colloidal substance 

 which however never fills the cavity of the alveolus. The wall of each 

 alveolus is formed of a single layer of epithelium. The whole may be 

 directly compared to the diffuse thyroid found in many Teleosts, as 



1) Biol, Centralbl,, Bd. 24, 1904. 



2) Anat. Anz., Bd. 8, 1893, p, 59. 



