424 



PROF. B. T. LOWNE ON THE STRUCTURE AND 



At this stage the ovary is pear-shaped '25 m. in diameter and 

 34 to '4 m. in length. It is enclosed in a thin but perfectly dis- 

 tinct cellular capsule (c). It consists of a stroma of small cells 

 less than 5 ^ in diameter, enclosing the bundle of egg-strings (e.s). 

 These are closely packed together and occupy the anterior rounded 

 half of the ovary. 



The posterior narrow part of the ovary (cl) is filled with small 

 round cells precisely like those which form the egg-strings, except 

 that the latter are slightly larger, 5 fx. 



Tlie egg-strings present, even at this period, a narrower con- 

 stricted posterior and a more dilated anterior portion ; they are 

 like long narrow flasks, the neck measures 5 /jl and the dilated 

 portion 15 /u in diameter. The whole consists of small closely 

 packed cells enclosed in a fine cuticular membrane. The necks 

 of the egg-strings appear to be open behind, where the cells of 

 the posterior part of the ovary, destined to form the duct, are con- 

 tinuous with those within the flask-like egg-strings. There is as 

 yet no trace of a lumen in the solid rudiment of the oviduct. 



The cells between and around the egg-tubes are, however, 

 already distinctly elongated and form a stroma, in which the egg- 

 strings lie, so diff'ering entirely from the cells which form the 

 egg-strings and fill the calyx of the ovary. 



The next stage of development is seen in the half-formed pupa, 

 about the tenth day (Plate XXYIII. fig. 5) ; at this stage the ovary 

 is apparently cup-shaped, it appears crescentic in lateral sections, 

 with the concavity of the crescent in front ; it has a diameter of 

 •5 m., but is still about '3 m. in thickness, measured from before 

 backwards in its thickest part. That part of the ovary not 

 occupied by the egg-strings is excavated by numerous chan- 

 nels ; these form the calyx of the oviduct and cover the whole 

 convex surface of the organ. The egg-strings are now so broad 

 in front that I shall term them egg-follicles. The egg-follicles (os.) 

 are ovoid masses of small cells, each with a very narrow stalk (st.) 

 The stalk is apparently filled by a single row of cells, and its 

 investing cuticle is frequently transversely wrinkled, which often 

 produces an appearance of striation. Possibly this may have 

 given rise to the very remarkable view held by Schneider (23) 

 that the egg-tubes are developed within the alar muscles of the 

 dorsal vessel. 



Each rudimentary egg-follicle is now surrounded by a pouch, 



