INTEEXAL ANATOMY OF BDELLA. 481 



which I have examined, I regret to say that I find myself unable to agree with Karpelles 

 as to several of the descriptions which he gives: tliese divergences of opinion will 

 be found detailed under the headings of the various organs as I come to them ; but 

 there is one matter which it is best to deal with here, as no such organ as that described 

 and flgvired by Karpelles will be found in my description. Karpelles shows an elaborate 

 endoskeleton in the abdomen, composed of numerous large and strong chitinous rings 

 and quadrangular frames pressed against or joined to each other, forming a very strong 

 and conspicuous apparatus. I can only say that I have dissected and sectioned and 

 carefully examined several hundred Bdclhe of various species and both sexes and of 

 various ages, but I never saw a trace of such an organ, nor have I ever found anything 

 of the kind in any Acarid ; but I have frequently seen, both in Bdella and other families, 

 in sections of the adult female the exact appearance which Karpelles figures and 

 describes; but in every case within my experience it has arisen in the following 

 manner:— When the eggs are ripe in the body of the female they are often very large, 

 and are in many genera, Bdella amongst others, provided with a strongly chitinized 

 chorion : in preparing specimens for section-cixtting it is extremely difficult to get the 

 paraffin or other embedding material to penetrate this chorion, it generally will not do 

 so ; the chorion, however, although chitinized, is not so extremely brittle as, for instance, 

 the exoskeleton of the Oribatidaj, and the razor cues it, forming rings and square frames 

 of chitin, whicl), as the abdomen in females with mature eggs is generally full of them, 

 press against each other and are fixed in the paraffin ; but the yolk and other contents of 

 the eggs, not being reached by the paraffin and therefore not being fixed, drop out unless 

 special precautions are taken to prevent it, when the precise appearance of Karpelles' 

 figure arises : but such special precautions can l)e taken, and if they be the yolk- 

 spherules are found filling the ring ; moreover, if the creature is dissected instead 

 of sectioned the eggs are, of course, found whole. I hardly like to suggest that 

 Karpelles may possibly have fallen into this error ; but the mistake is really an easy one 

 to make in a case like his : where no male has been found to act as a check it is the 

 more likely to have occiun-ed, so the paper referred to is, as far as I know, Karpelles' 

 first anatomical paper upon the Acarina, and therefore he may not have experienced 

 this difficulty before. If this be not the explanation, I am wholly unable to account for 

 his figure and description of this supposed endoskeleton. 



One other publication must be noticed as giving some little information regarding the 

 internal anatomy of Bdella. In Berlese's great work on the Italian Acari (r), which 

 is still publishing in fasciculi, the author, when he has finished "a group, writes an 

 introduction in which he gives type-plates of the respective families or subfamilies. In 

 his introduction to his order Prostigmata (Trombidiidte), Professor Berlese gives two 

 drawings of the rostrum and one or two adjoining parts of Bdella longirostris ; these 

 appear to be drawn chiefly from sections, althougli it is not so stated ; he does not say a 

 word about the internal anatomy in his letterpress, but he provides an explanation of 

 the plates, which gives the names of such internal parts as he draws. 



Although the above are aU the writings wliich I know of on the internal anatomy of 

 Bdella, yet as the BdelliniB are part of the great group of Acari which includes the 

 TrombidiidEE, Hydrachuidte, &c., the various works which have beeu published on the 



