104 MR. NEWPORT ON THE ORGANS OF REPRODUCTION, 



double, and also the excretory duct, for a short distance. In the female the ducts 

 are soon united, and continue so throughout their whole course, forming a single 

 large sac, covered externally with a large number of caeca, or ovisacs, in each of 

 which the rudiments of a germ are secreted. In the male the ducts continue single, 

 but communicate with each other transversely, thus forming a common cavity with 

 a double outlet, as in the female. Externally they are also covered with cseca, appa- 

 rently the analogues of the ovisacs ; for like them they contain their peculiar fluid, and 

 perhaps future spermatozoon that is believed to be essential to excite the development 

 of the germ in the female. This uniformity of the organs in the two sexes, is further 

 illustrated by the circumstance, that when the secretory process is complete, the fluid 

 passes into the large effcrential ducts in the male, as the ova are passed into the great 

 oviduct of the female. These parts agree still more curiously in the entire absence of 

 a spermatheca in the female, for the reception of the male fluid, and of distinct vesi- 

 culos seminales in the male, for retaining it after it is secreted, the want of which in 

 the former sex seems to indicate that the ova are deposited immediately after, or at 

 the moment of impregnation ; since, in true insects, in most of those instances in 

 which the ova are deposited quickly after the coitus, there is either no spermatheca, 

 or one that is but imperfectly developed. 



2. Structure of the Ovum. 



The existence of the ovisacs in lulus as single, isolated capsules, on the exterior of 

 the oviduct, in each of which a single egg is produced, is particularly favourable to 

 a minute examination of the ovum in all its states, especially as ova are found at the 

 same time in every stage of development (fig. 5. c c). The most rudimentary con- 

 dition of the ovisacs I have yet seen was observed on examining, by transmitted 

 light, part of an oviduct that had been placed for twenty-four hours in spirits of wine, 

 and afterwards dissected in water. In this (fig. 6.) the smallest ovisacs appeared like 

 very minute glandiform bodies, developed, as it were, directly from the structure of 

 the duct itself (c c), in which the rudiments of the future e^^ had begun to be pro- 

 duced. The smallest of these bodies were of an elongated shape, and not more than 

 three, or at most four, blood-globules in diameter. They appeared to have distinct 

 parietes, and to be filled with very minute graniform cells of a uniform size, slightly 

 opake, and of a yellow colour. The diameter of these cells, as nearly as I could 

 ascertain by direct comparison, was equal to about one third of that of a blood-glo- 

 bule. In the midst of these cells there was a larger, but much more delicate struc- 

 ture, of a circular form (a), and equal in size to about two of the cells, but whether 

 this was the proper germinal vesicle, or its macula, [?] it was diflScult to determine. 

 Other sacs in the duct, which were twice the size of these, were filled with similar 

 contents. From the opacity and yellow colour of these graniform cells, it was evi- 

 dent that they constituted the yelk in one of its earliest stages. I have never yet 

 seen these peculiar cells absent in any of the ovisacs, even in their most rudimentary 



