PERIPATUS GUIANENSIS. 147 



minute attention to details, however small and insignificant 

 they may be. Such measurements are not only useless, but 

 they are positively harmful^ for they are unconsciously being- 

 used as characters having considerable specific value, although 

 it is absolutely clear that from the point of view in question 

 they are of no importance. To arrive at this conclusion there 

 is no need but to consider the fact that in any collection 

 consisting of a fair number of individuals of a particular 

 species there are specimens the dimensions of which are at 

 least three times that of the smallest ones, although the latter 

 are as perfect as the former from the structural point of view. 

 The dimensions of any individual specimen depend on the 

 age of the animal at the time it was killed, and consequently 

 have no specific value. Again, the dimensions of a dead 

 Peripatus, to a great extent, depend on the method adopted 

 to kill the animal. Owing to the presence of circular, 

 longitudinal, and oblique muscles in the body- wall, a Peri- 

 patus measuring", when alive, about 80 mm. in length, is 

 capable, at death, of contracting itself to about 50, or even 

 40 mm. The amount of contraction taking place varies with 

 the reagent used, as well as with the degree of concentration 

 of that reagent. Consequently the dimensions of a dead 

 Peripatus, when giveu in a paper, do not increase the value 

 of the account, for they have no constant relation to the size 

 of the living animal, the length, depth, and width of which 

 vary according to the age of the individual under considera- 

 tion. 



In the third place, whether the legs are long and slender 

 or short and stumpy, and whether the successive pairs are 

 situated at a distance from or close to each other, are points 

 of no importance in a dead specimen ; nevertheless they are 

 carefully observed and recorded. If the specimen dies 

 fully extended the chances are that the legs are also fully 

 extended, and, in consequence, are long and slender, and 

 placed at a distance from one another ; but if the specimen 

 dies in a contracted condition the chances are equally in 

 favour of the legs being contracted, and, in consequence, of 



