212 WALTER GAESTANG. 



subject of bionomics (in Professor Laukester^s sense of the 

 word) should not receive more adequate recognition than it 

 does at present in the biological curriculum of our universities. 

 That such recognition would almost immediately produce 

 effects in a rapid extension of our knowledge is certain ; and 

 the subject is invested with so much intrinsic interest, as well 

 as with such important bearings on the problems of evolution, 

 that I believe such recognition would also have the effect of 

 attracting many students to the pursuit of morphology who 

 at present avoid it as a region of mere comparative anatomy. 



The present paper contains an account of some modifications 

 of form in certain exotic Crustacea upon which a new light 

 appears to be thrown by my recent researches upon the habits 

 of certain less specialised forms which inhabit British seas 

 (1896, 1897). My thanks are tendered at the outset to Pro- 

 fessors Lankester and Poulton for the facilities which they 

 have kindly placed at my disposal during my study of these 

 and numerous other forms of Decapod Crustacea. I am par- 

 ticularly indebted to Professor Lankester for the services of 

 his artist, Mr. Bayzand, from whose beautiful drawings ray 

 figures are copied. 



1. Calappa granulata, Linn. 



The figure (Plate 12, fig. 1) represents a front view of a 

 specimen of this crab as seen when lying flat upon a plane 

 surface. 



The genus Calappa is distinguished, among other points, 

 by the extraordinary size and shape of the chelipeds, which in 

 flexion are pressed tightly against the inferior surface of the 

 carapace, and by interlocking with one another form a sort of 

 buckler, the anterior and upper margins of which exactly 

 coincide with the anterior and lateral margins of the crab's 

 carapace. If the " hands" (propodites) of the chelipeds were 

 of the simple form usual among crabs, the anterior part of 

 the buccal apparatus would be visible even when the chelipeds 

 were pressed against the carapace, as is the case, for example, 

 in the species of Atelecyclus or in the species of Matuta 



