INTERNAL ANATOMY OP THE GAMASID^E. ^90 



thick fleshy, but probably slightly distensible, walls. At the point where the arras join 

 this portion the cells appear to separate from each other and become loose. This organ 

 exists in the nymph, but is then very small. When the female is adult, but lately 

 emerged, the lyrate organ, although much larger than in the nymph, is still not so large 

 as it will become ; it is when the impregnated eggs are attaining (one by one) the immense 

 size and highest state of maturity which they arrive at within the body of the mother, 

 that the lyrate organ is at its greatest size and development, but the cells of which it is 

 composed are not larger than, nor different from, those in the smaller gland. 



With regard to the function of the lyrate organ, I think that it must clearly be 

 regarded as a portion of the ovary. Speaking first of the arms only, they remind me in 

 many respects of the terminal chambers of the ovarian tubes in such Coleoptera as 

 Platysoma frontale, Hydrobius fuscipes, Byrrhus pilula, &c. It may of course he ques- 

 tioned whether they are the true germ-bearing portion, or whether they are composed of 

 vitelligenous cells only ; it is not perhaps easy at the present time to answer this question 

 with certainty, as biologists do not appear to be entirely agreed as to the office of what 

 are probably the most nearly allied structures in other creatures. Certain considerations 

 would at first seem to favour an idea of their being yolk-glands : these are inter alia, 

 firstly, their large size in creatures which do not appear to lay many eggs, but it is not 

 uncommon in nature for the number of germs in the ovaries to be enormously in excess 

 of the ova eventually matured ; secondly, the very large size and high state of develop- 

 ment which the egg attains within the body of the mother. In this and allied species 

 only one egg is really matured at a time, and the size and state of maturity which it 

 arrives at before deposition may be judged of from PI. XXXV. fig. 71, which is a sagittal 

 section carefully drawn to scale from an actual preparation of Holotaspis montivagus; in 

 the species I am describing, Hcemogamasus horridus,! think the mature egg is even larger 

 in proportion, but the embryo is not so highly matured within the maternal body. There 

 is generally a second, much smaller and natter, but still large, egg showing a moderately 

 forward state of yolk-division, but not any signs of the embryo forming. The other eggs 

 are usually much less advanced, although in various younger stages. 



Notwithstanding the above considerations I do not see any sufficient evidence of the 

 vitelligenous nature of the arms of the lyrate organ, and I think they must, at present 

 at all events, be looked upon as the germiniferous part of the ovary ; and this view would 

 bring the various organs of the female genital system most into harmony, and explain in 

 a reasonable and probable manner their relations to each other. As far as I know there 

 are not any structures in any other family of the Acarina at all resembling these lyrate 

 organs, so we cannot be guided by any analogy with other members of the order. 



The central domed elevation (cms), from the sides of which the arms spring, is, as 

 before stated, unlike them both in histology and otherwise : it is a hollow, shallow recess 

 with fleshy walls, and communicates with the arms, the portion of the ovary in which 

 the oocysts are developed and the eggs matured, with another organ to be mentioned 

 further on, and probably with the oviduct. It is occasionally empty, but is much more 

 frequently more or less filled with matter which closely resembles that found (as before 

 mentioned) in the spermatic capsule of the male Gamasus terribilis at the moment of 



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