Pai-asites are not at all easy to deal with; when taken out, everything — except 

 perhaps tolerably large females and ovisacs — must be kept in glycerine on an object- 

 glass, for if males, pupae, etc. are put in spirit, they are generally difficult to find and to 

 get out of the tubes. For this use the glycerine must always be strongly diluted with water, 

 otherwise the animals shrink very much, and the females especially are very apt to lose 

 their shape. The water is made to evaporate by standing exposed to the air. Neither the 

 females nor the males nor the animals in any stage of development, can bear the pressure 

 of a glass- cover, or of part of it, without losing their natural shape. In order to make 

 drawings of the entire animals or of parts of the females, the following method was employed : 

 I took very small covers (fi-equently a middle-sized cover was cut into foiu' parts), and 

 placed a very thin wooden wedge under the middle of the back edge of the cover, so that 

 by very carefully pulling the wedge a little, I made the glass touch the animal, or part of 

 it, just sufficiently to keep it in a certain position ; by means of a hair, which was introduced 

 through the opening, its attitude could easily be changed. In this way I was able after 

 some practice to manipulate a male of the length of Vfi mm. , so that I could make accurate 

 illustrations of one specimen seen from below and sideways without damaging it at all. 

 After use the animal and all the parts that had been examined were placed under a large 

 glass-cover in the way described above, and the o[)ening was closed with varnish. The 

 female was always dissected, in order to submit the head and the genital area to a careful 

 examination. The latter part was treated in the following way: with a sharp and very 

 small knife I cut through the animal a little above the genital region, after which this part 

 was placed under a simple microscope wliich magnified it a hundredfold; the inside of it 

 was cleaned with a knife, so as to leave only the muscles of the genital apertures and one 

 or both of the receptacula seminis. I specify this proceeding, which 1 learned by degrees 

 through rather troublesome experiences, partly that the reader may judge of tlie accuracy 

 of my illustrations, partly to enable future students, who may not possess such ample material, 

 to conquer the difficulties with comparative ease. 



As far as possible, I have everywhere given figures of an adult female, a male and 

 an ovisac (sometimes adding one or two pupae) magnified to the same scale, in order to show 

 the relative size of the two sexes, the ovisacs and eggs. The size of the male compared 

 with the female and the ova varies very much in the ditierent species. For the convenience 

 of the student, and in accordance with earlier statements (1890), I have always figured the 

 males vertically from the ventral side and laterally from the left-hand side. While in 

 symmetrically shaped Arthropoda, in dorsal or ventral view, I generally arrange the position 

 of the legs aud figure those on one side to correspond with those on the other, with the 

 parasites described in the present work I have not ventured to do this. ' The animals were 

 often a little crooked on account of a slight pressure, to which they had been exposed in 

 the marsupium; maxillipeds and legs were found sti'addling in different directions, and as a 

 rule were too small to allow of much alteration in their attitude, without great risk of 



