6 WRIGHT AND MACALLUM. [Vol. I. 



The subsequent removal of this from all except nervous tis- 

 sues, by means of potassium cyanide, as recommended by 

 Cybulsky and Delage, was attempted unsuccessfully, perhaps 

 on account of the slow penetration of the cyanide, which, while 

 decolorizing the outer tissues, leaves the central portions unaf- 

 fected. It is quite possible that a larger number of experi- 

 ments would have yielded some successful preparations, but we 

 were satisfied with the unfailing results of the method described 

 above. 



The process of imbedding selected was the chloroform-par- 

 affine method, the substitution of chloroform for turpentine 

 having been found to obviate shrinkage in the delicate cells, 

 to be afterwards described in connection with the excretory 

 system. 



Various aniline colors were used in addition to alum- 

 cochineal for staining the specimens in toto, but none gave such 

 uniformly good results as that medium. Many series of sec- 

 tions were prepared horizontal, transverse, and sagittal, and 

 mounted by Schallibaum's method in balsam or dammar. 



We have thought it best to outline the details of the tech- 

 nique employed in the present research, not only because the 

 histological results arrived at diverge in many respects from 

 received opinions, but also as a protest against the use of 

 material inadequately preserved by alcohol or other means as 

 the basis of histological descriptions. 



General Description of Appearance and Habits. 



On account of the dark color of the skin of the Meno- 

 branchs there is no difficulty in recognizing the presence of 

 their colorless ectoparasites. These are frequently found all 

 over the skin, especially on the inner surfaces of the legs and 

 along the back, and, indeed, on all places from which they can- 

 not easily be dislodged by the efforts of the host to free itself 

 from its tormentors. During the winter they have been 

 observed to be more frequent among the gill-filaments, and 

 such specimens do not seem to wander so freely as do the 

 larger summer individuals. That the Menobranchs are tor- 

 mented by the worms one realizes from their actions when 

 infested by several individuals, although their efforts to rub 

 them off can only be successful when the parasites attack the 



