512 Thkophilüs s. Paiktee, 



the work and for many helpful suggestions, but also for the use of 

 much material which he placed at my disposal. 



Material and Methods. 



Since male spiders, as a rule, function sexually only for one 

 season, it is desirable for studies in spermatogenesis to obtain 

 specimens as soon as they become mature. The season of sexual 

 maturity varies with the species.^) There is also considerable varia- 

 tion in the breeding season for the same species in difterent parts 

 of the country. 



Mature males can always be distinguished from the females by the 

 club-like form of the pedipalps. As is well known, in male spiders, the 

 pedipalps functions as a copulatory organ while in the female it 

 remains as a simple jointed appendage. For this reason, there is 

 never any difficult}^ in distinguishing the sex of a mature specimen, 

 but in young spiders this difficulty may arise, particularly in species 

 where the color scheme of the two sexes does not differ much. In 

 such cases, sectioning must be resorted to in order to determine 

 the sex, for the pedipalps of the male spider does not take on its 

 club-like structure until the second moult before the last. 



A number of killing fluids have been used in the present 

 research among which are Vom Rate's Platino-aceto-osmic mixture, 

 strong Flemming, sublimate acetic, Bouin's fluid and Petrunkevitch's 

 sublimate. All of these gave good fixation, but Petrunkevitch's 

 sublimate and Bouin's fluid were found the most satisfactory. The 

 Vom Rath fluid has one defect, in common with all liquids containing 

 osmic acid, namely, it tends to stain fat granules black. The subli- 

 mate acetic was discarded because it makes tlie chitin and the liver 

 of the abdomen very brittle and hard to section. 



The whole abdomen was preserved, after being cut open to 

 allow the fluids to penetrate, and the usual method of embedding 

 in paraffin was followed. Sections were usually cut at 5 /u, although 

 the thickness of the section was somewhat dependent on the character 

 and size of the individual specimen. 



In staining, Heidenhain's iron-haematoxylin has been relied upon. 

 Many other stains were used including Bismarck brown, thionin, sa- 



1) Emerton's book on "Common Spiders" will be found quite helpful 

 in determining the time of maturity of most of the common species. 



