STRUCTURE OF THE SHELL-GLAND. 



705 



The Shell- Gland communicates with the uterus at the bend above 

 referred to. It has the form of an ovoid or spheroidal body of consider- 

 able size (0'4 mm.), and is seated 

 on the convex margin of the bend. 

 In transparent preparations it can 

 be seen even with the unaided 

 eye. It lies in the middle line, 

 below the uterine coil, just before 

 the posterior margin of the joint, 

 at a position, therefore, where the 

 yolk -gland is situated in the 

 Tcenice. This fact contributed not 

 a little to the mistake I made in 

 the first edition of this work, in 

 identifying the two structures, and 

 in regarding the shell-gland of ^ 3 69. -Female reproductive organs 

 BotllTWCephoduS as the OVary, Under f Jiothriocephalus latus, seen from the 

 ,-, ., . ,T ,-, ventral surface. Between the two ovaries 



the erroneous supposition that the is geen the shell-gland. ( x 20.) 

 yolk-gland of the Tcenice produced 



the eggs. Nor did the histological structure of the body seem so 

 decidedly against my opinion, for Botticher, and at first Stieda 

 also, supported the same interpretation, although they both had 

 already recognised the true ovaries in Eschricht's "lateral glands." 

 They believed that the shell-gland, which had been also described by 

 Eschricht as the " knotted gland," and regarded by him as probably 

 serving for the secretion of albumen, was the median portion of the 

 ovary. In the appendix to his first contribution, Stieda> however, 

 recognised the true nature of the body. 1 



The parenchyma of the gland consists of a large number of pear- 

 shaped cells of 0*02 to 0'025 mm., enclosing clear or slightly turbid 

 contents, and each drawn out into a thin duct of considerable length. 

 The ducts are all directed inwards, and after a more or less straight 

 course, are all separately united with the loop of the fertilising canal. 



It is not strictly correct to speak of this complex mass of 

 unicellular glands as a spherical body, for not only is the centre of 

 the mass which is penetrated by the efferent ducts formed of 

 ordinary connective tissue, but there are no glandular cells on the 



1 Moniez has lately reproduced the old mistake, He regards the shell -gland as a 

 special median portion of the ovary ( " ovaire central "), in which, however, the ova never 

 attain maturity, but become abortive. Only the lateral ovaries produce eggs. After 

 liberation, they pass into a cavity in the parenchyma between the ovaries, are received in 

 the adjacent funnel or trumpet-like muscular end of the oviduct (" pavilion de 1'oviducte "), 

 and passed onwards. The fertilising canal and oviducts are not united with the uterus 

 till some distance from the Uterine receptacle. 



2 Y 



