402 REPORT ON ZOOLOGY, MDCCCXLIV. 



researches in respect to the cuticular animalcule of Simon, Researches into 

 the structure and development of a newly-discovered parasitic animalcule of 

 the human skin, the E/ttozoonfolliculorum. (Philos. Trans. 1844, p. 305.) 

 The author has met with both the forms observed by Simon, the long one 

 with the hinder end blunt more commonly, the short one with the same 

 pointed more rarely, and has traced a different course of development in 

 each. The eggs are bodies of considerable size, and the author having 

 failed to discover any corresponding particles in the abdomen, after examin- 

 ing many hundreds of these creatures, he thinks that he finds an earlier 

 condition of them in a cluster of nucleated cells [vesicles] within the hind 

 extremity of the abdomen, and is confirmed in this view by meeting with 

 little masses of such cells in the neighbourhood of the animalcules, and along 

 with these, somewhat larger cells composed of subordinate small ones, and 

 others more or less oval in shape, which contain within the investing mem- 

 brane subordinate nucleated cells of considerable size and varying in number. 

 These last he considers as a form of transition to the proper egg, which is 

 oval, semitranspareut, amber-coloured, composed of nucleated cells, and 

 encompassed by a thin transparent membrane, and measures in the greatest 

 diameter, ^ to ^ g th of an inch. The contained cells are so arranged as to 

 compose an oblong body bent at each end (the embryo). The author has 

 not seen the bursting of the egg, but has found newly-hatched embryos, 

 and the cast egg-membranes. After this the embryo continues to develop 

 itself, becoming thinner at the ends, while the hinder extremity is length- 

 ened out considerably, and at last legs appear in the thick part, and oral 

 organs at the fore end. Such is the process with the long-bodied sort ; in 

 the other the mouth and legs show themselves externally, while the embryo 

 is still inclosed in the egg, and the lengthening of the abdomen takes place 

 at a later period. Both sorts have at first but three pair of legs, the fourth 

 appears after a moult. The development of both, as described by the 

 author, presents so much that is extraordinary that it will require particular 

 verification, and at least partial correction, before it can be received. 



As respects the internal structure, the author has not been more success- 

 ful than his predecessors in discovering any definite organs. In regard to 

 the external anatomy he thinks he has made various discoveries, e. g. not only 

 of eyes, but an eyering (orbita), four [pairs of] labral palps, and three (!) of 

 labial. The region of the mouth, which is very limber, he treats as a head 

 retractile within the thorax, and the abdomen as divided into segments, 

 although, in fact, the appearance of numerous narrow rings on the abdomen 

 is owing merely to the texture of the skin, and there is no trace of proper 

 articulation. With such misconceptions, the author's ideas as to the 

 systematic place of the subject cannot but be confused, and in truth he 

 tramples down every principle of Zoology, when he attributes to it palps and 



