466 



have been tiglitly pressed against it, now eventually com- 

 municate with its cavity. At this time, also, two outgrowths 

 are formed from the posterior portion of the vagina; one 

 grows very rapidly and extends backwards within a few 

 hours to a length of about one-third that of the abdomen. 

 Already at this stage it has an extremely narrow lumen, and 

 consists entirely of embryonic cells, similar to those of the 

 vagina. The other outgrowth is considerably shorter, never 

 exceeding half the length of its fellow. Structurally the 

 two are the same at this stage ; I shall speak of them here as 

 the "accessory glands." 



At this time, also, a pair of distinct thickenings are 

 seen, one on either side of the antero-dorsal part of the vagina. 

 They will develop into the "lubricating glands" of the adult 

 (fig. ,184). They are composed of very elongated cells, 

 arranged irregularly in two ill-defined lines. 



Meanwhile the ovary has commenced to grow forwards, 

 but this forward growth is accompanied by a curious parti- 

 tioning of the whole ovary. The layer of small cubical cells 

 covering it, and the overlying serosa begin to grow inwards 

 at the tip of the ovary, in such a way as to divide the whole 

 organ into four distinct compartments (fig. 192). 



As the ovaries continue to extend forwards the newly 

 formed portion must likewise possess this four-chambered 

 appearance. On the other hand, an extensive back-growth 

 of these partitions eventually divides the whole ovary and 

 even a considerable portion of the oviduct, into these four 

 characteristic chambers; indeed, only the terminal portion of 

 the oviduct, adjacent to the vagina, remains devoid of parti- 

 tions. During the next two days the ovary grows forwards 

 on either side of, and above, the intestine, and, in the 

 advanced pupa eventually terminates slightly behind the 

 anterior wall of the abdomen. 



In the twenty-four hour pupa, meanwhile, a new process 

 of partitioning of the ovary has commenced. Ingrowths of 

 the protecting membranes of the ovary divide the anterior 

 tip of each of the four chambers into three secondary parts. 

 The partitions do not extend deeply, but each ovary as it 

 grows forwards now breaks up, as a result, into twelve 

 papillae; these elongate rapidly and form twelve ovarian 

 tubules, which comprise the anterior end of each ovary (see 

 fig. 180). 



The ingrowth of the external parts of the ovary becomes 

 very pronounced in the oviduct of the pupa of about two 

 days, being now in the form of a great connective tissue 

 stroma, with four channels, each lined by a layer of flat 

 cells, running along it. 



