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



This class of border, although I do not remember its having been described, is fre- 

 quently found on the movable genital plates of the Gamasinae ; and is attached to the 

 lower (ventral) part of the edge where the plate is movable, so that it lies under and 

 close against the ventral surface ; but it is usually so fine and transparent that it cannot 

 be seen until the plate is lifted. 



In H. horrid us there is not a trace of the chitinous structure of G. crassipes inside the 

 epigynum, nor is there any sign of the domed recess which practically functions as a 

 spermatheca in G. crass'tyes: the vagina (PI. XXXV. fig. 68, va) is an extremely simple 

 chamber, with soft and thin walls, leading without vaginal glands or other complication to 

 the oviduct ; I have not even found spermatozoa or spermatocysts in it. There is not here 

 any marked difference between uterus and oviduct ; the whole appears one organ without 

 distinction of structure or constriction between, unless it be considered that in this and 

 allied species the whole represents Winkler's uterus, and that his oviduct is here sunk in 

 the ovary, which would be a theory requiring some evidence. I have therefore used the 

 expression " oviduct " for the whole (figs. 49, 68, od). The oviduct leads to the ovary 

 (figs. 48, 49, 68, ov), which is placed near the ventral surface and much as in G. crassipes, 

 and may be said to fairly agree with the same organ in that species, except in being 

 rather smaller, more flattened, and less regular in form ; it fades into the oviduct without 

 its being easy to say exactly where one commences and the other leaves off, although 

 there is a considerable constriction between the two, through which a tracheal trunk 

 passes. The oviduct runs backward and forms a kind of pocket (PI. XXXIV. fig. 49). 



Now commence the un described organs. In the centre of the ovary on its upper 

 surface is a rounded elevation which does not show actual eggs developing ; from the 

 sides of this elevation spring two great paired flattened arms or branches ; the Avhole 

 structure, including the root and two arms, is somewhat lyre-shaped, and I propose 

 calling it " the lyrate organ " (organum lyriforme) *, and shall so speak of it in future ; 

 it is irregular in form, never quite agreeing in two individuals or on the two sides of the 

 same individual, but still preserving the same general form in each species ; so that, 

 after becoming well acquainted with them, it would, I think, be possible to tell what 

 species a dissection was from by the form of the lyrate organ alone. This organ is one 

 of the largest and, as regards the arms, one of the most solid in the body ; it stains 

 deeply and is wholly composed of largish clearly-marked cells averaging about 30 n 

 diameter, without any intercellular space or tissue ; each cell has a well-defined nucleus 

 averaging about 7 n diameter, but I have not been able to see nucleoli with certainty. 

 The size and appearance of the cells and nuclei is extremely regular all over the surface 

 of the organ, except just near the root, where the cellulation is lost : if the organ be cut 

 into sections the interior cells are found to be similar to the exterior ; the cells are 

 not larger near the root than at the distal ends of the arms, nor are the nuclei more 

 distinct or larger in one place than the other. A portion of one arm of the lyrate organ 

 of a closely-allied species, Hcemogamasus hirsutiis, is drawn on a larger scale, fig. 47, in 

 order to give an idea of the cellulation, &c The central rounded elevation from which 

 the arms arise does not exhibit the same cellulation and is not solid — it is hollow, with 



* The full uame should probably bo the lyriform portion of the ovary, but I use " lyrate organ " for brevity. 



