On tlie couiiective tissues and body cavities of tlie Neinerteiins. 33 



Multipolar anrl l)ipolar mesencbym cells are found in this cavity, with 

 tine, branching fibres; their nuclei are of the general size and 

 appearance of those of the previously described tissue, but as a rule 

 stain less intensely. At occasional intervals, small groups of niesen- 

 chym cells may be found, producing short, peripheral layers, bound- 

 ing the body cavity ; and, rarely however, their nuclei show evidences 

 of amitotic (?) division. As we have seen in AmpJiiporus, the main 

 difference between the mesencbym and the previously described connec- 

 tive tissue, is to be found in the denser intercellular substance of 

 the latter. 



3) Parenchym tissue is quantitatively more reduced than in 

 any other species which I have examined. It is absent in the head 

 and oesophageal regions, and occurs around the proboscis sheath, 

 only from about the middle of the latter, to its posterior end. The 

 layer of parenchym cells, which even posteriorly is not more than 

 from one to three cells deep, forms only a semicircle around the 

 ventral periphery of the sheath, nowhere encircling its dorsal peri- 

 phery. At those points where the dorsal blood vessel lies immediately 

 below the proboscis sheath, its dorsal surface comes into contact with 

 this layer of parenchym cells; but no cells occur around the dorsal 

 vessel behind the rhynchocoel, nor anywhere around the lateral vessels. 

 The structure of the cells is the same as in AmpMporus. 



4) The intracapsular connective tissue of the central 

 nervous system is very much reduced in amount, even more so 

 than in AmpMporus virescens; the cells apparently resemble those of 

 the species just mentioned, though their smaller size renders them 

 very difficult of study. They stain very faintly, are without pigment, 

 and apparently multipolar. Their nuclei are usually smaller, more 

 elongate, and stain less intensely than those of the ganglion cells. 

 Since these cells occur mainly between outer and inner neurilemma, 

 and very seldom in or around the fibrous core, I cannot say whether 

 more than one modification of them occurs. 



5) Interstitial connective tissue of the body epi- 

 thelium. In my previous paper (90 a, p. 100, fig. 8), I have de- 

 scribed this tissue as follows: ''Seine Kerne sind meist rundlich, von 

 0,003 mm Durchmesser und enthalten je einige grössere Nucleoli 

 (more properly, chromatin masses). Jeder Kern ist von einem sich 

 mit Carmin färbenden Plasmahof umhüllt, von welchem zarte, mit 

 einander anastomosirende Fasern nach allen Richtungen hin verlaufen. 



Zool. Jahrb. X. Abth. f. Morph. 3 



