480 ME. A. D. MICHAEL OX THE 



Ammonia, compared with the five distinct palpal joints, foiir eyes, and hairy claws 

 pulvilli) of Bclella. 



The anatomy in this paper is of the genus Bdella only ; I have not had the opportunity 

 of studying that of Ammonia. 



The Bdellinse are sharply distinguished from all other Acari by their antenniform, non- 

 raptorial palpi, ending in hairs. 



Karpelles (8), working upon Bdella arenaria, Kramer, which is supposed to he 

 identical vdth Bdella vulgaris ^Hermann), states that the Bdellinse are exclusively 

 (" ausschliesslich ") vegetable-feeders, and that the remains of mosses are found in their 

 alimentary canal ; he also states that certain black matter often found in their canal is 

 earth. I regret to say that I entirely disagree with him ; in my opinion all Bdellinse 

 which I have studied have been predatory, living entirely by sucking the juices 

 of other small creatures, principally Thysanuridae, which they capture with their 

 mandibles. 



Bdella Basteri lives in chinks in the rocks of the sea-coast, and emerges when the 

 tide goes down ; often at those times it is abundant upon the decaying seaweed, feeding 

 on the Thysanurida? which swarm there. Trouessart, in his classification of the 

 Acarina (20), says that the Bdellinse are " terrestrial Acari feeding upon living prey " ; 

 and this eminent acarologist informed me by letter that he found that they lived greatly 

 upon Thysanuridse, an opinion which he formed quite independently of my own, and 

 mthout knowing that I took the same view ; and he states that Poduridse are the food 

 of B. Basteri {sangidnea) in his paper on that species (21. p. 125). It may also be 

 remembered that the name " Bdella " is a pure Greek word, signifying a leech, so that 

 it is tolerably evident what Latreille's opinion was. Pinally, the trophi, and indeed the 

 alimentary canal also, appear to me to be characteristic of a predatory animal living by 

 suction and not of a vegetable-feeder. Karpelles himself says that the matter j)assed by 

 the anus (as to which organ see below, p. 490) is liquid, and that he never found 

 excrement balls, which scarcely seems quite consonant with his view that the vascular 

 bundles of plants are found in the canal. 



The internal anatomy of Bdella may practically be considered an almost, if not wholly, 

 new subject. The external anatomy and the trophi are described by Kramer (11); 

 his descriptions, although not very full, are in my ojiinion almost always correct, so far 

 as they go : therefore in this paper T have not referred to the external anatomy, except 

 very shortly in one or two instances, where it seemed necessary in order not to break the 

 continuity of study of organs which terminate at the exterior of the creature. 



The only paper which I am aware of that touches on the internal anatomy of Bdella 

 is that by Karpelles (now Karell) before referred to (8). It is very slight indeed*. 

 In the first place, Karpelles did not find the male, and therefore does not say anything 

 about the male genital organs ; but it happens that it is in this set of organs that the 

 greater part of the most sti'iking variations which distinguish the internal anatomy of 

 Bdella from that of all other Acari which I know of exist. In the next place, unless 

 Bdella arenaria (if really different from B. vulgaris) be very different from every Bdella 



* The whole nervous system and sense-organs occupy only about 20 lines, the respiratory organs about 4 lines, &c. 



