192 iiB. A. D. MICHAEL OX A^ [Mar. 5, 



to ascertain with certainty whether this tube euds blindly or is the 

 duct of a fourth salivary gland ; my opinion is that the latter is 

 correct and that the tube is a fine duct coming from a small 

 roundish gland lying close to the reniform gland. It is for this 

 reason that I say above " at least three pairs of salivary glands," 

 but as I have not been able to trace the comnmnication with 

 certainty I have thought it best not to draw this gland. The 

 common duet runs to the upper surface of the chitinous bridge or 

 lamella which is joined at its edges to the inner sides of the maxillary 

 lip and forms a chitinous endo-skeleton in the rostrum upon which 

 the mandibles rest. The commom duct penetrates this chitinous 

 bridge, and runs forward for a short distance practically within its 

 substance ; the duct terminates by a bell-shaped mouth (cZ6.) on 

 the underside of the chitinous bridge. 



In addition to the paired glands above described, there is an 

 azygous sausage-shaped gland (fig. 23, asg.) practically in the 

 median line of the hind part of the rostrum. It is about -ll mm. 

 long, with a diameter of about -02 mm., is a fieshy organ with an 

 extremely small lumen, and lies between the paired fan-shaped 

 groups of muscles which run from the sigmoid piece to the 

 mandibles (see page 203). The duct from this gland is short and 

 hue, and runs straight forward towards the buccal chamber. 



I have said above that I doubt whether there is sufficient 

 evidence to justify us in asserting positively that the function of 

 all these various glands is salivary only. 



The Male Genital Organs (Plate VIII. figs. 17, 18; 

 Plate iX. figs. 23, 28). 



The male reproductive system differs in a remarkable degree 

 from anything which has, to my knowledge, been hitherto described 

 among the Hydrachnidse, or, indeed, in any of the allied families. 

 Schaub, for instance, in his species found a group of five pyriform 

 testes on each side discharging by a common duct, which duct 

 joined \^'ith its fellow from the opposite side to form a short 

 unpaired duct leading into a long, much convoluted, duct, which 

 he calls the vas deferens : this terminated in a short penis 

 surrounded by muscles. Croneberg's Eylais shows a complicated 

 network of testes entirely unlike anything found in the present 

 species. Probably the nearest described organs are those of the 

 species of Trombidium figured by Croneberg in his later work, 

 ' Ueber den Ban von Trombidium ' ; but even these present most 

 material differences from the form I am about to describe. 



In Tliyas petropliilus there is, on each side of the body, what 

 appears to be a large testicular mass (figs. 17, 28, 23, T.), which 

 . immediately underlies the lateral portion of the ventricular ring. 

 This testicular mass has an average length in fuUy-formed speci- 

 mens of about '3 mm., by a thickness in a dorso-ventral direction 

 of about '17 mm. in its thickest part. This mass is comparatively 

 flat on its under (ventral) surface, and comparatively, although 

 not quite, straight on its inner side ; but it is formed into two 



