UROGENITAL SYSTEM OF MYXINOIDS 103 



whether he thought they belong to the pronephros or to the meso- 

 nephros. Kirkaldy seems to consider the Malpighian body as 

 belonging to the head-kidney. Semon ('96) thinks it is the first 

 Malpighian body of the mesonephros. Spengel ('97) is of the 

 opinion that this is, in fact, the glomus of the pronephi'os in Myx- 

 ine. From his investigation of very young Myxine Maas ('97) 

 concludes that it is the glomus of the pronephros formed by the 

 'concentriren' of the most posterior 'Gefassnetze' which surround 

 the original segmental pronephric tubules. Price ('04, '10) re- 

 gards this Malpighian body in Bdellostoma as belonging to the 

 'pronephros,' and from embryological study concludes that it 

 arises by the fusion of glomeruh which are formed in connection 

 with some of the most posterior original tubules of the pronephros 

 before they are crowded together by the posterior movement of 

 the gills. Since, in the embryo, only two or three of the original 

 tubules which take part in the formation of the head-kidney 

 have glomeruh, then the definitive pronephros represents the 

 fusion of not more than two or three glomeruli. 



The adult condition of the Malpighian body in Myxine and 

 Bdellostoma supports the conclusions of Maas and Price in regard 

 to the manner in which it is formed. The pronephros of both 

 shows evidence of being the result of fusion of two or three glom- 

 eruh. The following description is for both Bdellostoma and 

 Mjodne, and any variations which either shows will be noted. 



The Malpighian body is always located beside the posterior 

 half of the pronephros, usually at the extreme posterior end. It 

 is always imbedded in the connective tissue beside the pronephric 

 vein and is separated from the pronephros by the sheath of its 

 Bowman's capsule and the pericardium, as well as by a more or 

 less wide strip of the pericardial cavity (fig. 39). Quite fre- 

 quently the Malpighian body is followed immediately by a sec- 

 ond, the anterior end of which may lie beside the last few tubules 

 of the pronephros (fig. 12). Ordinarily, however, this second 

 Malpighian body is located back of the posterior limits of the 

 pronephros. The capsules of the two Malpighian bodies shown in 

 figure 12 are connected by a very narrow duct, the short colum- 

 nar cells of which do not have as much cytoplasm as those of the 



