388 THOS. H. MONTGOMERY jr., 
It is to Vespovsky that we owe the most important interpretations 
of Gordiacean structure. But the fact that his conclusions have not 
been generally accepted by the later workers has led me to make 
the present study, primarily to learn for myself what the facts of 
structure are. VEJDOVSKY’s observations I can corroborate in most 
particulars; in regard to certain points of the anatomy I have been 
able to add to his account, particularly in regard to the structure of 
the nervous system; and in the interpretation of the affinities of the 
group I have reached somewhat different results. The contributions 
of Vespovsky mark a new epoch in the study of these forms; and 
since he has reviewed the literature bearing upon the anatomy and 
embryology, I shall not repeat this review, and in the discussion of 
different opinions upon mooted points, which are placed at the end 
of the description of each organ, I shall not go back in the literature 
beyond the time of the first paper by VespovsKy. In thus not con- 
sidering the literature in detail previous to 1886, I intend in no way 
to undervalue the labors of earlier investigators; it is surely not 
necessary that each new contribution should give abstracts of all 
papers that have preceded it; and in regard to the genus Paragordius 
there is no previous anatomical literature, Gordius and to less extent 
Chordodes being the subjects of investigation. A nearly complete list 
of papers on the Gordiacea has been compiled by CAMERANO (1897). 
In regard to methods of study, it is to be noted that but little 
can be determined by clearing the whole animal in oil, owing to the 
opacity of the body wall. Almost all the following observations were 
made upon sections of 6?/, u thickness, both transverse and longi- 
tudinal. ‘Thinner sections than these cannot well be made owing to 
the hardness of the cuticle. It is necessary to imbed short pieces of 
the animal in hard paraffine for about an hour and a half. Serial 
series of sections through the head and tail regions, and through 
various intermediate regions of the trunk, were made of different in- 
dividuals. 4°/, formalin I found to be an excellent fixative, the best 
employed; corrosive sublimate solutions give very poor fixation, and 
the osmic acid fixatives do not penetrate in time to prevent the 
tissues from macerating. All the staining was done upon the sections 
on the slide; the double stain, DELAFIELD’s haematoxylin followed by 
aqueous solution of eosin, gave very good results, but by far the best 
stain for sharp definition and especially for studying the nerve and 
muscle elements was the iron-haematoxylin method of HEIDENHAIN. 
In addition to the preceding methods, hand dissection was employed 
