BY N. A. COBB. 453 



accurate and well executed figures of both extremities of each 

 worm described. The dimensions given, based sometimes it is 

 true on too few or otherwise too imperfect measurements, related 

 to the length, breadth, position of the vulva, depth of the buccal 

 cavity, and the fraction of the entire length occupied by the tail 

 and oesophagus respectively. To these Bastian added the dimen- 

 sions of the spicula and strife. The English author, making the 

 inch his unit of length, contented himself with giving a categorical 

 list of the measurements made. Thus, taking a species at random, 

 Enoplus pigmentosus was entered as |^x ^^j teeth, -^-q', oeso- 

 phagus, about y {i.e., of the total length) ; tail, y^-^. This is 

 manifestly not very convenient for the reader. The German 

 author, making the millimeter his unit of length, followed the 

 same plan as his English contemporary but gave fewer measure- 

 ments, trusting no doubt that the exquisite figures accompanying 

 his text would supply all necessary information concerning details. 

 Biitschli, the renowned Heidelberg naturalist, followed (1873-4) 

 the plan adopted by Bastian and Eberth, but brought to his aid a 

 greater amount of pictorial art. His illustrations are full length 

 porti^aits, accompanied by figui'es on a larger scale, the latter 

 illustrating the details of the head, tail, &c. Marion (1873) 

 furnished no new ideas to the nomenclaturist. De Man, however, 

 has introduced decided improvements in nomenclature. Bealizing 

 the necessity for exactitude and completeness in the matter of 

 measurements, this author, who has described a greater number of 

 new forms than any of his predecessors in the same field, and 

 added also very essentially to our knowledge of the Nematode 

 anatomy in general, has adopted a series of ratios by which a 

 considerable number of measurements are expressed very concisely. 

 These ratios he represents by the Greek letters a, /3, y, — his a being 

 the ratio of the length to the median (greatest) diameter, /3 the 

 ratio of the total length to the length of the oesophagus, and y the 

 ratio of the total length to the length of the tail. Thus, after 

 having given the absolute length, he is enabled to give three 

 remaining dimensions by means of such an expression as the 

 following : a = 45, (3 = 5, y = 8. 



