DEVELOPMENT AND IMMATURE STAGES. 181 



to all families of Acarina; he asserted that at each 

 ecdysis all the internal organs liquefied and became 

 reduced to a sarcodic plasma enveloped by a veritable 

 blastoderm ; which behaved like that of the egg, and 

 sprouted in the same manner. By some error Megnin 

 attributed this supposed discovery to Claparede, who 

 for a considerable time had the credit of it in the 

 writings of subsequent authors ; but in reality Clapa- 

 rede never said so, and Megnin apparently over- 

 looked the fact that it was Gudden who had announced 

 it. Subsequent investigation has, however, shown that 

 the theory is not correct ; and that the return to a 

 more or less amorphous condition is usually, and 

 probably always, confined to the soft parts of the legs 

 and trophi, and what may be described as appendages or 

 external organs. Kramer* soon expressed doubts 

 about the correctness of this theory ; which was shown 

 to be erroneous in the Trombidiidae by Henkin,t and 

 by others in different groups ; and by Nalepa in 

 the careful account of the ecdysis in one of the Tyro- 

 glyphidae, of which the following is an abstract. J 



Nalepa observed the ecdyses in Garpoglyphus anony- 

 mus, he says correctly that the larvae and nymphs of 

 that species, like those of other Acaris, fall into an 

 inert and motionless state before each ecdysis. In this 

 condition they do not take nourishment, they lie with out- 

 stretched legs in wet parts of their habitat. The first 

 glance shows the atrophy of the lime and fat so 

 largely contained in the connective tissue. Later on 

 a rapid increase in the number of cells in the hypo- 

 dermal tissue may be observed : the hypodermis, which 

 has hitherto shown a reticulated appearance, takes on 

 an epithelial character, and thus returns as it were to 

 an embryonic condition. In the connective tissue 

 large, fine-grained cells appear, the origin of which 



* " Ueber Milben," ' Z. ges. Naturw.,' 1881, Bd. liv, p. 12. 



t " Beitrage zur Anatomie, Entwicklungsgeschichte, und Biologie 

 von Trombidium filiginosum, Herm.," in ' Z. wiss. Zool.,' 1882, Bd. 

 xxxvii, Heft 4, p. 569. 



J Nalepa, Anat., 2, pp. 149157. 



