34 THOS. H. MONTGOMERY, 



Dieses Gewebe ist viel mehr als die Stützzellen der Hauptträger des 

 Pigmentes, welches in Massen in seinen Fasern vertheilt ist."' 



X. Comparisons and Conclusions. 



From these investigations on Carinella, Cerebratulus , Lineus, 

 Amphiporus , Tetrastemma and Stichostemma, the following general 

 conclusions may be drawn: 



1) The connective tissue with dense intercellular substance, the 

 parenchym, and the intracapsular tissue of the nervous system occur 

 in all these genera. 



2) I find a true mesenchym tissue only where there is an evident 

 perivisceral body cavity, namely in Cerehratulus , Carinella, Lineus 

 gesserensis (absent in L. lacteus), Amphiporus and Stichostemma, it is 

 absent in Tetrastemma. 



3) A pigmented connective tissue without intercellular substance, 

 situated in the body muscular wall, is possessed only by Lineus. 



4) The branched connective tissue cells with a more or less 

 dense intercellular substance compose always the basal membrane of 

 the body epithelium, as well as the basal membranes of all other 

 epi- and endotheha (of the blood vessels, nephridia, proboscis, and 

 rhynchocoel, but not that of the intestine) ; it also constitutes typically 

 the elements between the muscle fibres or muscle bundles. This tissue 

 reaches its greatest quantitative development in the Metanemertini, 

 forming in this group a thick sheath separating the intestine from 

 the longitudinal muscle layer, this sheath enclosing the nerve chords, 

 lateral vessels, and gonads. This tissue in all the forms constitutes 

 also the neurilemmatic layers and threads of the nervous system; and 

 produces the inner sheath of the nerve fibres. 



5) The true parenchym tissue, under which term I understand 

 walled cells (being the only Nemertean connective tissue cells provided 

 with membranes), without intercellular substance and extraneous cell 

 fibres, and which are largely filled with a structureless fluid, — this 

 parenchym tissue reaches its greatest quantitative development in 

 Carinella and Cerehratulus. In the former genus, this tissue occurs 

 around the proboscis sheath, dorsal side of the intestine, and lateral 

 vessels even behind the rhynchocoel; in the latter genus, around the 

 proboscis sheath, and dorsal and lateral vessels and their commissures ; 

 in both these genera the parenchym cells form a complete mantle 

 around the blood vessels, in the anterior region of the trunk. In 

 Lineus and the Metanemertini, the parenchym tissue is absent 



