IIQ S. GOTO. 



the niediim line. The cells, especially of the ventral groups, are far 

 removed from the ootyp ; and they are therefore provided with long- 

 efferent ducts, whicli open into the ootyp after making more or 

 less windings on the way (PI. XVL, fig. 4). In Trist oiiiiuii also, the 

 shell-glands are far removed fr(3m the ootyp, and open by means of 

 long ducts into its very beginning (PL XXII, fig. o). In some 

 species of this genus (c. (j. Trist, sinuatam) the wall of the <>otyp sends 

 out a few small, tubular evaginations, into which the shell-glands open 

 (PI. XXII, fig. 6). In Mouocotijli' too, these glands are j)i-ovided with 

 long stalks, and open only at the beginning of the (jotyp. 



As to the shell-glands themsehes, they are in most s{)ecies of an 

 irregular pohgunal form. The nucleus is more or less \esicular and 

 contains one or a few nucleoli ; the ])rotoplasm is usually gnsnular, 

 stains well, and is wholly destitute of any external membrane. The 

 glands, however, (jften appear like small naked nuclei, owing to the 

 shrinkage of their protoplasm. This condition is evidently owing to 

 exhaustion, and corresponds to the period of complete rest. In Moiio- 

 Cijtijlc the shell-glands are ellipsoidal or spherical, and are, as already 

 stated, provided with l«jng stalks (PI. XMTI, fig. 1). The nucleus, 

 which contains in this case usually a single nucleolus, occupies a more 

 or less eccentric position, and the cyto[)lasm is finely granular and 

 stains weakh'. The ducts are on the «jther hand often filled with a more 

 dee])ly staining, and more coarsely granular substance ; the cytoplasm 

 and the contents of the du(,'t being s(jmetimes separated by a sharp 

 line (PI. XVIII, fig. 1). I do not know what interpretation to put on 

 this phenomenon, except to regard these goblet-shaped cells as having 

 arrived at tlie culminating point of their secretory activity and to have 

 almost entirely emptied themsehes of the product oï secretion, leaving 

 only the [)roto[)lasm in the body of the cell — in other words, I regard 

 the deeply staining contents of the duct as the })roduct of secretion, and 



