HARD WICKE ' S S CIE NCE - G SSI P. 



20I 



of this rare parasite, which, it will be seen, is not 

 unlike a Menopon. 



7. Gyropus. — This, which is the last genus, also 

 ■contains two species, both of which are found on the 

 guinea-pig, and are not uncommon. The one, G. 

 gracilis, is long and narrow, the other, G. ova/is, 

 short and broad. They are small parasites, and look 

 to the naked eye very like small pieces of straw. 



I have now run very rapidly and imperfectly over 

 the various kinds of Anoplura, and hope that my 

 description and illustrations will be sufficiently clear 

 to enable any one to classify any specimens he may 

 have, and thus give zest to the study of parasites, a 



Fi/. 127. — Head and 

 part thorax of Phy- 

 sostomum of Chaf- 

 finch. X 60. 



Fig. 128. — Eureum of Sivift. 





J 



i*t?Sjggp 



SJBH- 





Fig. 129. — Gyropus of Guinea Pig, cf. X (o. 



study the interest of which is, I am sure, surpassed 

 r Dy no field of science. 



All the illustrations, with two or three exceptions, 

 are photographed from specimens in my own cabinet, 

 and are chosen with a view of showing typical 

 examples of each genus. 



In deference to the views expressed by the Editor 

 in the August part of Science-Gossip, I now add a 

 few words regarding the collection and preparation 

 of animal parasites. 



As regards the collection of specimens, it may be 

 Aruly said that parasites are to be found everywhere, 

 as species infest almost every living creature. In the 

 case of birds, the parasites will generally be found on 



the barrels of the feathers, which should be turned 

 back one by one. 



Some species, such as the Docophori, are most 

 plentiful about the head, while others are most 

 abundant on the wings. The species of the genus 

 Dermaleichus look like fine dust, and are most easily 

 seen by looking through the feathers at a strong light. 

 Parasites may frequently be found on dried skins 

 as well as on newly-killed birds, and when placed in 

 turpentine or glycerine generally regain their former 

 shape and size, though, in such cases, we cannot rely 

 implicitly on this result being attained. As a rule, 

 parasites are not found so plentifully on mammalia as 

 on birds, and blood-sucking species must be looked 

 for while their hosts are yet warm, as they leave, 

 apparently, as soon as the blood begins to cool ; this 

 is especially the case with fleas. 



As regards the preparation of specimens, not much 

 requires to be said. The best method for scientific 

 investigation is undoubtedly to mount in cells, in 

 glycerine, though for micro-photographic purposes 

 this process is unsuitable. The usual method of 

 mounting in balsam, if carefully carried out, need 

 not to any great extent injure the specimens. If 

 possible, caustic potash should not be used, and care 

 should be taken not to flatten the object by pressing 

 down the cover on the slide. My usual method is to 

 soak the parasites, for a shorter or longer time, 

 according to their size and colour, in turpentine, then 

 place them on the slides, lay the glass cover over 

 them, and allow the babam (dissolved in chloroform) 

 to run in. The resulting slides would look better if 

 cells were used, as the covers would then be quite 

 flat. Some of the minute Acari are much too trans- 

 parent if mounted in balsam, and for these, glycerine 

 is the proper medium, thin cells of varnish being 

 necessary. 



If caustic potash must be used, caution is required 

 not to carry it too far, and produce specimens which 

 are mere ghosts, so to speak — a fault which I have 

 found by no means uncommon, even amongst pro- 

 fessionally-mounted slides. 



ON THE VARIATION AND CONTINENTAL 

 DISTRIBUTION OF THE BRITISH SLUGS. 



By J. W. Williams, D.Sc, etc. 



[Continued from p. 148.] 



T IMAX CINEREO-NIGER, Wolf. — This 

 X— • species is generally distributed over the Con- 

 tinent, but is said to be rare in England, where it 

 has no doubt been often described as a variety of 

 Limax maximns, Linn. In France, Bourguignat has 

 recorded it from the Nord and the Isere ; Lallement 

 and Servain from the Aisne ; Baudon from the Oise ; 

 Mabille and Jousseaume from the Seine-et-Oise and 



