452 SUMMARY OF CURRENT RESEARCHES RELATING TO 



adapted for walking are now seen. The " fundamental trait " in the 

 phylogenetic development of this group presents a very striking 

 analogy to what is seen in the Vertebrata. 



The side branches are no less interesting; singular as is Pagurus, 

 with its soft tail enclosed in a shell, Lithodes and Birgiis are still 

 more specialized. In the Penteidse the buccal and ambulatory appen- 

 dages are closely connected ; the second and third maxillipedes do 

 not differ from these latter. In the Brachyura there has been central- 

 ization and sjjecialization ; the mouth-organs differ much from the 

 ambulatory limbs, the first of which are specially modified to form 

 an organ of prehension. " The superior forms are, then, when com- 

 pared to the inferior, centralized, and their different parts are 

 si^ecialized." 



These studies of M. Boas will doubtless have an important influ- 

 ence on carcinology ; no abstract can give an idea of the elaborate and 

 detailed accounts which he gives of the forms which he has examined, 

 and many of which he has figured. There are altogether 216 figures. 

 Latin diagnoses of the groups and genera are given, and the whole is 

 almost more than summed up in the French resume with which the 

 essay concludes. 



Change of Colour in Crabs and Prawns.* — Dr. Fritz Miiller 

 contributes some instances of this phenomenon — already discovered 

 by H. Kroyer — from the Brazilian fauna. 



The shrimp Atijoida potimirim, of the sub-family Atijime, has a 

 female which when adult and living among water-j^lants is usually dark 

 green, sometimes inclined to blue or brown, occasionally of a pure blue 

 with a pale brown streak down the back ; when put into a glass vessel 

 it fades to an increasingly pale brown, which disapj^ears and leaves 

 the animal colourless and transparent in the course of a few days ; 

 a dark brown sijecimen placed with a number of others which had the 

 usual greenish hue assumed their colour in a few minutes. A black 

 Palcemon taken from deep water became first dark, then pale blue, and 

 the colour, losing its even distribution, became accumulated in many 

 closely-packed patches ; after half a day from the time of capture it 

 had lost all colour, with the exception of the caudal swimmeret, which 

 remained blue. The male of a small land-crab, Gelaslinus, whose 

 carapace is marked with pure white and light green, loses these 

 colours when captured, and they are replaced by a uniform grey. 

 The variations in coloui' of the swimming crab Naut'dograpsus are 

 due to temporary changes of colour according to circumstances, and 

 are not rightly explained by Moritz Wagner as being permanent, and 

 as leading the individuals to frequent those beds of seaweed which 

 harmonize with their particular colour, a conclusion which is 

 further opposed by the record given in the ' Challenger ' report of the 

 different surroundings in which the same crab may occur, a fact which 

 implies a change of colour. This and similar instances of variation 

 are better explained by the view of segregation, than by that of the 

 migration of the differing forms. 



* KosmoB, viii (1S81) pp. 472-3, 



