HYFOPID^E. 



235 



Hypopus filicum. 

 Copied from Dujardin. 



CASE side of the abdomen are the suckers by which it attaches itself. 



XIV. ^ 



Subsequently, M. Dujardin found other species on other insects, 

 but still without understanding them any better ; at last, in the 

 month of September, while searching for Tardigrades on mosses 

 and fern (Ceterach officinarum), he found a Hypopus in sufficient 

 abundance, very similar to the other, but quite distinct, and which 

 lived fastened by its suckers on the shin- 

 ing leaves of that fern, as the other is 

 fixed on the polished coats of insects. 

 But one very remarkable thing came 

 under his notice in studying this mite, 

 namely, that amongst those that he so 

 observed several were narrower, more 

 transparent, and completely empty; 

 some, much more rare and completely 

 immovable, showed in the interior 

 another form of mite, soft, and curled- 

 up like an embryo, and occupying the 



whole of the internal cavity of the Hypopus, as if the latter 

 had been the shell of an tgg^ but of an egg living and provided 

 with feet, as the nympli of flies is contained in the shell formed 

 of the hardened skin of the larva. The little mite inside had, 

 according to Dujardin, palpi and chelate mandibles like the 

 Gamasi and Dermanyssi, and he thence arrived at the conclu- 

 sion, that these Hypopi, without mouth, without possible means 

 of growth, living fixed by their suckers on polished surfaces^ 

 from which no nutriment could be derived, must be larvae, or 

 rather, if the phrase were allowable, eggs furnished with feet, 

 and endowed with motion, in the interior of which, without 

 aliments derived from without, the young Gamasus had to form 

 itself at the expense only of the nourishment contained within. 

 Consistently with this view, Hypopi should be found wherever 

 the Gamasi live, and he maintains that that is just what is the 

 case. On Geotrupes, Necrophonis, and Humble bees, which are 



