290 MR. A. D. MICHAEL ON THE VARIATIONS IN THE 



There is not any intromittent organ known in the Gamasinse ; the ductus ejaculatorius 

 communicates directly with the exterior hy a roundish opening (PI. XXXIII. figs. 29, 

 31, 33, ga), which, in most genera, is placed in the median line immediately in front of 

 the sternal plate, and thus in the soft cuticle which is found hetween that plate and the 

 hypostome, i. e. the ventral side of the oral tube (or rostrum). Immediately in front of 

 the genital opening is a curious narrow flap of chitin truncated and terminated by 

 two slightly feathered setaj (figs. 2 & 36, bp) ; it is hinged by its proximal edge to 

 the cuticle, is hollow, and has a fine nerve distributed to it. It is found in both sexes, 

 although the female genital aperture is distant from it. Kramer calls this organ the 

 breast-palpus ; Winkler considers it to be the homologue of a labium ; I feel doubtful 

 about this homology, and therefore speak of it in this paper by the neutral name of 

 "thebipilate appendage." It is usually found in the Gamasinse, and does not cover 

 the genital aperture. 



The genital organs of the male of Gamasus terribilis are delineated by fig. 29 ; a 

 glance at that drawing will show how widely they differ from those of Winkler's species : 

 that difference is not in any degree a question of time of year or surrounding circum- 

 stances ; I have examined the organs in large numbers of specimens at all seasons, but 

 invariably with the same result. The unpaired, globular, central testis is entirely 

 absent ; in its stead we have two very large doubly-pyriform organs, L e. each testis is 

 more or less of the shape of two pears with their thick ends placed together ; but the 

 hinder pear stands somewhat perpendicularly, and leans and curves inward and somewhat 

 forward, while the anterior pear lies nearly horizontally, but curves inward. It must 

 not be supposed that these two pear-shaped pieces are in any way separate organs; they 

 are thoroughly continuous ; only there is an external, not very deep, rounded constric- 

 tion at the point where the somewhat perpendicular part ceases and the horizontal 

 commences. The hinder and upper ends of the two bilaterally symmetrical testes are 

 joined together by a very thin connection near the dorsal surface, just in the situation 

 (as regards the genital organs) where the single testis is in Winkler's sj^ecies ; although 

 in that species, with its long vasa deferentia, the testis is much nearer the anal end of 

 the creature. It will be seen from the drawing that the long, thin, well-marked vasa 

 deferentia of G. crassipes are not to be found in G. terribilis ; indeed, vasa deferentia can 

 scarcely be said to exist at all in the latter species : a minute portion of the organ on 

 each side, close to Die ductus ejaculatorius, may be called a vas deferens ; but there is not 

 any real demarcation between that and the testis. Of course it might be said that the 

 whole horizontal portion of the organ, on each side, was a vas deferens ; but the form of 

 that part, its entire continuity with the hinder part of the testis, the solidity of its 

 contents, and their steadily progressive development from the hinder to the anterior end 

 of what I call the testis seem against that view. 



The ductus ejaculatorius and the great accessory gland are practically similar to those 

 of G. crassipes, except that the former is perhaps a little longer in proportion, and not 

 quite so uniform in diameter as in G. crassipes ; and that the latter is without the 

 curious narrow recurved portion at the posterior end figured by Winkler. 



Doubtless, in spite of the extreme dissimilarity between the above described organs in 



