On the connective tissues and body cavities of the Nemerteans. 19 



Wandung des Rhyucliocöloms eingeschlossen ist." But had Bükgek 

 seen the marked structural distinctions of the several kinds of connec- 

 tive tissues, and had he classified them according to these dillerences, 

 he would have found, that the true [»arenchym tissue always envelops 

 the dorsal blood vessel and the ventral i)ortion of the proboscis 

 sheath, though it may be absent on the lateral vessels and the com- 

 missures. And we have learned that the parenchym cells lining the 

 lateral blood vessels of Carinella, do not lie anteriorly in the body 

 cavity, but between the muscle fibres, as is also the case in Lineus. 



4) The intracapsular connective tissue of the cen- 

 tral nervous system. This consists of usually multipolar, and 

 seldom bipolar (as BtiRGEU, '90, states for other species), membrane- 

 less cells, whose exceedingly fine fibres form a loose network around 

 and between the ganglion cells (Figs. 11, 14). Around the nucleus 

 is a mass of finely alveolar cytoplasm. The nucleus (Fig. 14) is very 

 variable in size and shape; it is usually flattened, and oval or 

 elongate-oval in outline ; the outline is also usually irregularly notched, 

 or angular; frequently nearly spherical, conical, sickle- or spindle- 

 shaped nuclei are found. In fact, these nuclei are more variable in 

 shape than those of any other cells in the body; though the nuclei 

 of the muscle cells (especially of the circular layer of the body wall) 

 are also noticeably variable. Especially characteristic is the com- 

 paratively large amount of nuclear sap, causing the nucleus to stain 

 much less deeply, than that of any of the ganglion cells, or than that 

 of any other connective tissue. One nucleolus (Fig. 14 n) is always 

 present, of a spherical form, and staining with eosin (with which the 

 true chromotin does not stain) ; sometimes two nucleoli occur, both of 

 which may be situated centrally, or at opposite poles of the nucleus. 

 Small masses of chromatin are distributed peripherally, apposed to 

 the nuclear membrane, a small mass also surrounds the nucleolus, 

 while chromatic fibres pass from this central mass to the peripheral 

 layer; thus the arrangement of the nuclear chromatin is more or 

 less reticular. No evidences of cell divisions are found. 



Three modifications of these intracapsular cells may be distin- 

 guished : 



a) Cells containing a finely granular pigment, yellowish in color, 

 which may be present in small masses near the nucleus, but is 

 more usually finely distributed along the cell fibres (Fig. 14). These 

 cells occur only in the brain-lobes, between the outer and inner 

 neurilemmatic sheaths. They are especially numerous on the dorsal 



