Further Notes on British Oribatidm. By A. D. Michael. 3 



instance, Huxley,* talking of the Acarina, says : " Most are 

 oviparous, but the Orihatidse are viviparous." This statement, in 

 spite of the high authority for it, is certainly an error, although 

 there may be a few exceptional instances of it, as will be seen later 

 on in this paper, but those instances are, as far as I am aware, 

 recorded here for the first time. The impression which has got 

 abroad among naturalists, and held its ground so tenaciously, is, 

 perhaps, the more curious, because Nicolet, the principal author who 

 has written upon the Orihatidse, says that the egg is deposited, and 

 that the larva emerges very shortly afterwards, and this dictum of 

 the French aoarologist, in my opinion, correctly states what really 

 occurs in a great many, and probably in the large majority of 

 instances. 



The result of my own observations has been to convince me that 

 the matter is not quite so simple as naturalists have supposed, and 

 that it is not possible to lay down one general rule which will be 

 correct in all cases ; indeed, this remark is applicable to most ques- 

 tions connected with Acarina. 1 have usually found that if I have 

 attempted to generalize from a few known instances the rule which 

 I thought I had found has broken down, and I have also found that 

 a great number of the general laws enunciated by other observers 

 fail to stand the test of a wider experience. 



It seems to me that there are at least three if not four modes by 

 which the eggs are brought to maturity, and the larvae hatched, in 

 difierent species, or under different circumstances. 



The first method is that so well known in insects, that the egg 

 is deposited in a fertilized but only slightly developed state. The long 

 ovipositor, or extensile oviduct, of the female Acarid is used for this 

 purpose, and the egg is placed in crevices of the wood, moss, or 

 fungus, upon which the larva will feed ; the egg adheres, either by a 

 certain viscid quality in its exterior envelope, or more often is 

 attached by a few threads of silk-like substance. Segmentation may 

 have gone on in the egg to some extent before deposition, but very 

 little progress has been made towards the differentiation of any in- 

 dividual parts of the future larva. A very considerable time often 

 elapses between the deposition of the egg and the hatching of the 

 larva in this mode, and I think that the creature probably often 

 passes the winter in the egg state, and is only hatched on the 

 approach of spring. I have frequently had the eggs myself for a 

 long time before hatching in various species, as, for instance, 

 Damseus geniculatus, D. clavipes, Nothrus thelejproctus, &c. 



The second mode is that which Nicolet apparently considered to 

 be universal, and which I myself believe to be the most frequent, 

 particularly in full summer. This is, that the development of the 



* 'A Manual of the Anatomy of Invertebrated Animals.' London, 1877, 

 p. 383. 



B 2 



