32 DOUBLE MONSTROSITY— IN CARTILAGINOUS FISHES 



and cut up, about thirty living young escaped from its abdomen. The specimen presented lived for 

 about two days in a bucket of water. 



Klaussner (123 p. 12) makes mention of an instance in which there were two embryos on 

 opposite sides of the egg of a cartilaginous fish. The record was given verbally to him by Dr. Riickert. 



Longitudinal or Parallel Union. Dohrn (57) describes and figures an interesting malformation 

 in an embryo of Torpedo marmorata, one mm. in length. The specimen, which had been cut into 

 horizontal sections, shows two notochords lying parallel with one another, and a short distance 

 apart. 



The mesoblast on the outer side of each notochord is normal in arrangement and shows division 

 into seven muscle somites. Between the notochords is a narrow unpaired strip of mesoderm with 

 eight separate somites, forming a series which is out of line with the normal lateral ones. Details 

 are given regarding the size, etc., of the somites, but the condition of the nervous system and of the 

 alimentary canal is not described. 



Parasitism. No definite instances seem to be on record, but the suggestion is not an unreason- 

 able one that the accessory fins noted by Gervais (80) and Rennie (203) in the skate are remains of 

 rudimentary twins (see p. 54). 



