274 Seientific Proceedings, Royal Dublin Societ//. 



According to Qlaser's recent observations ('13) there is a difEerence in 

 attitude between the two species of Hypoderma when laying eggs : H. lineatum 

 holds the ovipositor nearly parallel to the skin of the beast selected as a 

 host, while H, bovis pushes lier ovipositor almost vertically down among 

 the hairs. 



The Malk Eepiioductive Organs. 



1. The Testes and their Ducts. 



The internal reproductive organs of the male are of the type usual in the 



Diptera, and require no lengthened description. We have not been able to 



dissect a fresh male of Hypoderma lineatum. In H. bovis, the testes are small 



reddish pyriform bodies (Plate XXIV, fig. 20, Te.), each 125 mm. long and 



•65 mm. broad at the wider anterior end ; they have firm, thick walls. 



Posteriorly the testis tapers, and passes into a slender ras deferens (fig. 20,V.d.), 



about 3 mm. in length. At the point where the two vasa deferentia unite is 



situated a small ovoid accessory gland (fig. 20, A. G.), 1 mm. long ; this would 



be identified by some anatomists as a seminal vesicle, but Lowne ('95, p. 662) 



states that the corresponding (paired) structures in the Blow-fly never contain 



spermatozoa, and calls them paragonia, while Bruel ('97) regards them as 



prostate glands, and describes their secretion. Similarly situated organs in 



several genera of Diptera are described as accessorial glands by Keuchenius 



in his recent memoir ('13). From the junction of the vasa deferentia 



a slender median ejaculatory duct (fig. 20, D.e.) passes backwards. After a 



course of about 5 mm. it enters the ejaculatory sac (figs. 20, 22, S. e.), which 



is "35 mm. long, and has a chitinous lining, with a remarkable solerite, the 



ejaculatory apodeme, developed in its wall. This structure has in both species of 



Hypoderma, when viewed from the side, a heavy, rounded front end, and a 



more slender, hooked hinder end. In H. bovis, however (PI. XXIV, figs. 21, 22), 



the front end is slightly swollen, and the hinder end has two prominent recurved 



hooks ; in S. lineatum (PL XXV, fig. 30, S. e.) the front end is far heavier, and 



the hinder end has a comparatively feeble single hook. When viewed dorsally 



or ventrally (see figs. 20, 26, S. e. ; the latter is drawn from a specimen in 



which the ejaculatory sac has been turned on its axis through a right angle), 



the apodeme in both species is seen to be broad at both ends, and somewhat 



constricted in the middle ; tlie hooks must, therefore, be shaped rather like 



scoops. The duct from the testes enters the sac at its ventral face — farther 



forward in H. hovis (fig. 22, D. e.) than in H. lineatum (fig. 30). The sac is 



continued backwards into the terminal part of the ejaculatory duct 



(fig. 30, D. e.), which travei'ses the penis, 



