136 E. W. MAOBRIDE. 



by a close network of interlacing fibres. Intermingled are cells 

 whose bodies stain slightly differently from the general plasma 

 of the organ. In fig. 2 dl have drawn some curious nuclei from 

 the ovoid gland of another adult, which seem to me to point at 

 direct cell division. In the extension of the organ towards 

 the nerve-ring the plasma gradually disappears, aud it takes 

 on the form of the ordinary connective tissue ; but there seems 

 to me to be no reason to regard the spaces in this as in any 

 special sense lacunae. In the part which is enclosed by the 

 sinus a some cells are seen with larger and better defined 

 bodies than in other portions of the gland. These are 

 Hamann's '' Urkeimzellen/' primitive germ-cells, of which the 

 genital rachis is also composed. Their meaning will be under- 

 stood when the genital rachis is treated of. 



II. Development. — Fig. 3 represents a section (in the 

 standard direction) through an embryo about '2 mm. in 

 diameter. The stone canal is seen lying in the middle of a 

 mass of cells which take the place later occupied by the coelom ; 

 the thickening on the inner side of the canal is an indication 

 of the presence already of the ampulla. Unfortunately the 

 other sections of this series are somewhat broken in this place, 

 and in my other series of the same stage the stain was not 

 good enough to give a clear figure of this cavity. I have no 

 doubt, however, that it exists at this stage.^ 



Russo (17) has mistaken the mass of cells filling the coelom 

 for the rudiment of the ovoid gland, but the next stage (which 

 I have obtained at least half a dozen times) clearly shows 

 his error. Figs. 4 a, b, c, represent three consecutive sections 

 3^ ju thick through a slightly older embryo (the size is not an 

 exact guide to age). As these three sections comprise the whole 

 stone canal and surrounding rudiment of the gland, the import- 

 ance of dealing only with perfect series of very thin sections 

 will at once be perceived. 



A single layer of nuclei {ps.) lining the coelom, which there- 

 fore can be called peritoneal, can be seen in fig. 4 b covering 



> Since writing the above I have seen the Ampulla not only in embryos of 

 this age, but also in bilateral larvae. 



