AND THE DEVELOPMENT OF THE MYRIAPODA. 103 



Birds, some ova being always fully developed, and ready to pass into the oviduct, 

 while others are in various stages of development, many of which are imperceptible, 

 excepting with the aid of a powerful lens. 



But the most remarkable condition of the female organs is their double vaginal 

 outlet {a a), as in Crustacea, although the oviduct itself is a single tube until near 

 its termination (6), where it is divided into two short canals, which, from a slight 

 opacity at their base, where they join the single duct, appear, when seen by transmitted 

 light, to be separated from it by a valve, or duplicature of the lining mucous mem- 

 brane. The vaginal orifices (a a) are simply two nipple-shaped portions of the tegu- 

 ment, with somewhat oval apertures, surrounded by a corneous ring, from which is 

 developed a circle of minute hairs. Internally these apertures are closed by a soft 

 thickened membrane : they are situated on the under surface of the fourth segment 

 of the body, and correspond in that to the insertions of the legs in the third segment. 



In their general structure the organs of reproduction in the female lulus present 

 some analogies to those of Meloe and Forficula among insects, in which the single 

 ovisacs are arranged on the outside of a large oviduct, into which all the matured 

 ova are passed, to be deposited at one act, as in lulus ; but they differ from these 

 genera in the structure of their vaginal outlets being double, as in Crustacea and 

 Arachnida-, and differ again from the last in the remarkable fact, that throughout 

 nearly its whole extent the oviduct is a single sac, and divides only into two canals, 

 one of which passes on each side of the nervous cord, immediately before it arrives 

 at its termination. It is difficult to give a reason for this peculiar conformation. 

 May it be connected with a necessity for great rapidity in the act of depositing the 

 ova required by this singular tribe of Invertebrata, the only apparent explanation of 

 this peculiarity ? 



The situation of these organs beneath the alimentary canal, and their separation 

 from it by the interposition of the adipose tissue, extended in the manner of a peritoneal 

 coat, has already been stated. This adipose tissue, formed of vesicles filled with fat, 

 as in insects, is most extended in the course of the muscular bands that pass down 

 from the dorsal vessel, on each side of the segments, until they arrive at the upper 

 surface of the oviduct. In the course of these bands there seem reasons for suspect- 

 ing that vessels also exist, as they are proved to do in the Annelida ; and that the 

 ovaries are supplied, by these means, with the circulatory fluid directly from the dorsal 

 vessel. The division of the dorsal vessel at its anterior part into distinct vessels, and 

 the connexion of these with a large vessel extending along the upper surface of the 

 nervous cord in Scolopendra, as seen both by Mr. Lord* and myself-f-, strongly sup- 

 port this opinion. 



The simplicity of these organs in lulus beautifully exemplifies the remarkable 

 similarity of structure which the labours of anatomists have shown to exist between 

 these parts in the two sexes. In both male and female the outlet to the organs is 

 * Medical Gazette, March 3. 1838, vol. xxi. p. 892. t Ibid. March 17, 1838, p. 970. 



