434 



PEOF. B. T. LOWNE ON THE STRUCTTJRE AND 



With regard to the histology of these glands, very little, if 

 anything, can be said to have been recorded of a satisfactory 

 character. Stein gives several very remarkable figures (I. c. 

 pi. ix. figs, i, V, and xii) of their histological structure, with the 

 following description : — 



" The fine structure of the glands is nearly the same in all 

 Beetles ; they belong to that class of glands which yield a 

 fluid secretion, and which are tubular, follicular, or exhibit 

 bladder-like cavities. In the gland-follicles the proper elements 

 of the gland form a manifold layer of nucleated cells which pre- 

 pare the secretion. Between these cells very fine wavy canals 

 spread into the follicles, formed as outgrowths of the epithelial 

 coat (of the central cavity), and terminate either in blind ends or 

 within the cells*. 



" In general the contour of the gland-follicles is the same as 



that of the epithelial coat of the central cavity The 



secreting-cells lie hetween the epithelial and 'peritoneal coats [the 

 italics are mine] without order, near and over each other, and 

 not united together. In form they are round, oval, or egg- 

 shaped ; in the latter case the blunt end is turned outwards, and 

 the outlines of the cells, when one examines the entire follicle 

 under a certain pressure, are not generally distinctly seen, so 

 many lie over each other, and the cells, owing to their granular 

 contents, are so opaque " (pp. 102, 103). 



Leuckart (16«), in his memoir on the Pupiparse, gives a 

 figure of the corresponding gland of 3£elophagus ovinus, which, 

 although on a much smaller scale, represents a similar appear- 

 ance, and gives a description which corresponds nearly witli 

 Stein's. 



These figures and descriptions are very diificult to understand, 

 excejDt on the supposition that both Stein and Leuckart examined 

 glands with a quantity of adherent fat-cells. The fat-cells of the 

 ovary form a large mass on its posterior aspect, and closely sur- 

 round and adhere to the gum-glands. These fat-cells, when half 

 empty, as they always are in the egg-laying female, exhibit 



* "Zwischen diesen Zellen verbreiten sicb am Follikel sehr feiue geschlan- 

 gelte Kanale welche von Austulpungeu der Epithelealhaut gebildet werden, und 

 die nach aussen entweder blind endigen, oder an einer Zelle endigen." 



