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Show 378 MR. F. E. BEDDARD ON THE [Apr. 1 9, Perrier's figure (loc. cit. pl. ii. fi?. 26) ; Perrier places the the same segment as that which contains the external orifice, and is so far in accord with myself; but the oviduct is represented as lying behind the ovary instead of in front of it. In one of the two specimens which I investigated by means of sections, I found a body corresponding exactly in position to the ovary in the majority of Lumbricidae ; a pair of small cellular bodies exist on the anteiior mesentery of segment 13 near to the ventral median line ; the-e bodies are composed of small indifferent cell*, and resemble very closely the testes of the same worm; each of these is surrounded (Plate XXXIII. fig. 4) by a muscular sac which is continuous with a duct; the duct appears to open into the duct of the spermatheca opposite to the orifice of the glandular diverticulum; I succeeded in tracing it forward nearly to this point, but did not observe its actual orifice. The cellular body was attached to the mesenteiic wall, and was entirely free from its enveloping muscular sac ; this fact, as well as the evident immaturity of the gland, naturally suggested that the connection with the duct was secondary. Three were no traces of cilia in the duct. These glands occupy a position exactly corresponding to that of the te.tes, i. e. just above the venti almost setae, while the ovary of segment 14 has a similar relation to the dorsal setae (see woodcut, fig. 1, p. 381). It might easily, therefore, be suggested that the structure on the 13th mesenteiy is the true ovary, and that the supposed ovary in the next segment is really the equivalent of the receptaculum ovorum. The position of the different organs referred to is in accord with such an interpretation; that is to say, their po-ition so far as concerns the segments which they occupy. The position of the several structures within the segment, however, differs : the glandular body of the 13th segment corresponds exactly with the testes (see below, p. 381, fig. 1) ; a straight line connecting the testes and the glandular body of the 13th segment wotdd run exactly parallel with the long axis of the body ; on the contrary the ovaries of the 14th segment are placed much further away from the ventral median line of the body, and are placed not very far from the female geneiative pore. Tins alteration of position, however, may have been produced during the growth of the ovary and its duct; and in any case it is a fact which may be used with equal force as an argument either for or against the supposition that the ovaries of segment 14 are ovaries or receptacula. The principal arguments in favour of regarding the ovaries of segment 14 as real ovaries are :- (I) The fact that the ova undergo their whole course of development in those bodies ; indifferent germinal cells can be traced through all the intermediate stages into fully developed ova. The receptacula of other Earthworms, on the contrary, contain only adult or nearly adult ova. (2) The presence of rudimentary ovaries (?) in segment 13, whose structure and relation to their duct suggests how the continuity between the supposed ovary and its duct of segment 14 may have been |
