24 THOS. H. MONTGOMERY, 



and ventral aspects of the rhynchocoel, and the dorsal side of the 

 dorsal blood vessels (Fig. 23); but it is certainly absent around the 

 lateral vessels and their commissures — differing in this point from 

 Cerehratuhis. The parenchym cells around the rhynchocoel are not 

 epithelially arranged, but as in Carinella, occur more or less isolated 

 among the fibres of its circular muscle layer, as well as on the 

 periphery of this layer (Fig. 23); and since the cells are seldom 

 massed together, they have usually a spherical instead of a polyhedral 

 form (cf. Cerébratulus). The dorsal blood vessel has not a peculiar 

 envelope of parenchym cells, but, lying immediately beneath the pro- 

 boscis sheath, its dorsal surface is in contact with the parenchym 

 cells of the ventral periphery of the latter. These cells are similar 

 in structure to those of Carinella. 



5) The intracapsular connective tissue of the cen- 

 tral nervous system (Figs. 27, 29). The distribution of this 

 tissue is as in Cerébratulus^ being the supporting tissue par ex- 

 cellence of the ganglion cells, and to some extent also of their 

 fibres. The membraneless cells are bi- or multipolar, with exceed- 

 ingly fine, branching fibres; pigment is absent. The nucleus stains 

 more faintly than those of the ganglion cells; and its chromatin is 

 finely distributed in the achromatic sap (Fig. 29), not producing a 

 network as in Cerehratulus ; further, the nucleolus is comparatively 

 smaller, and occurs in a smaller percentage of cells than in the last- 

 named genus 0- Though the nucleus varies greatly in size, some 

 being even twice as large than those of the largest ganglion cells, 

 as is never the case in the other species examined; those found be- 

 tween the outer and inner neurilemmatic sheaths are pretty generally 

 oval in form, few being angularly notched or elongated (cf. Cere- 

 hratulus). Occasional dumb-bell-shaped nuclei are found, but without 

 previous increase in size, such as is always the case in the other 

 connective tissues; so that it is doubtful whether these forms of the 

 nuclei represent division stages. The nucleoli are proportionately 

 small, and rare in occurrence, whereas the opposite is the case in 

 the corresponding cells of Cerehratulus. Two modifications of these 

 intracapsular cells may be distinguished: 



a) Those situated between the outer and inner neurilemma, in 



1) Can there exist any physiological relation between the size 

 of the nucleolus, and the manner of distribution of the chromatin? 



