A STUDY IN CARCINOLOCa'. 65 
observation and experiment of such complicated functions as those dealt with 
in the foregoing paragraphs if there were not very clear evidence that such 
an anterior inhalant current as I have described does in fact exist. One 
such piece of evidence is afforded by the matted feltwork of hairs covering 
the ventral surfaces of the expanded anterior extremities of the exopods of 
the first maxillipeds. These hairs lie flat and point backwards : they are as 
evidently laid back by a current of water passing over them as the sea-grass 
on the mud-banks of an estuary is laid back by the tide that has swept over 
it. Again, in most examples of Ranina a considerable amount of sand is 
entangled in the setse with which both the exopods and endopods of the 
second maxillipeds are abundantly furnished. This gives evidence that these 
appendages are bathed by a current of water not wholly freed from sand- 
particles by the filtering apparatus of the orbits and antennae. But perhaps 
the clearest evidence of all was furnished by the large Ranina sent me by 
Prof. Kishiiioye. In this specimen the inner surfaces of the third pedun- 
cular segments of the antennae; the ventral surfaces of the exopods of the 
first and second maxillipeds, the inner surfaces of the mastigobranchs of the 
first maxillipeds, the proximal part of the mastigobranchs of the second 
maxillipeds, and the bases of the podobranchs of the second and third maxilli- 
peds were infested by numerous small pedunculate cirrhipedes belonging 
to some as yet undetermined genus and species of the family Lepadidaj. 
In other words, these intruders had established themselves along what I 
have described as the course of the incurrent respiratory stream, but none 
were to be found in the upper part of the gill- chamber, nor on the scapho- 
gnathite, nor on any part of the walls of the exhalant canals. It is evident 
that their larvse had been swept by the incurrent stream into the inhalant 
chamber, and had subsequently fixed themselves in positions where the adults 
could obtain a constant supply of nourishment borne by the incomino- current. 
But, where the currents were setting outwards, conditions were unfavour- 
able and none had established themselves. 
From what precedes, it follows ihsii Ranina, no less than A^ofojjwi, is highly 
adaptable in respect of its respiratory arrangements, and can make use 
of different mechanisms as the circumstances of the moment may require. 
When half buried in loose sand or when wandering on the surface these 
animals probably respire through tlie apertures at the posterior end of the 
thorax. When deeply buried in compact sand they are forced to rely on the 
antennary apparatus. In point of efficiency and specialisation their 
respiratory mechanisms fall far short of those exliibited by other " Oxysto- 
matous" crabs, the Leucosiidae, the Calappinse, and the Matutinte, but 
adaptability to varying conditions implies a high survival value, and it is to 
be remarked that Notopus and Ranina are among the oldest of the fossil 
Raninidae. 
LINN. JOURN.— ZOOLOGY, VOL. XXXV. 5 
