ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
20 $ 
connective tissue wliich aids in healing the fragments. The intestinal 
epithelium changes in character as it takes up its new external position. 
The whole process of fission has evident relationships to the process of 
reproduction. 
Connective-Tissues and Body-Cavities of Nemerteans.* — Dr. T. H. 
Montgomery, jun., has investigated species of Carinella , Cerebratulus 
Linens , Amjohiporus , Tetrastemma, and Stichostemma , and draws the fol- 
lowing general conclusions : — 
The connective tissue with dense intercellular substance, the paren- 
chyma, and the intracapsular tissue of the nervous system, occur in all 
these genera. A true mesenchyme tissue was found only where there was- 
an evident perivisceral body-cavity. A pigmented connective tissue with- 
out intercellular substance, situated in the muscular body wall, is possessed 
only by Lineus. The branched connective tissue cells with a more or 
less dense intercellular substance form the basal membranes of the 
epithelia and endothelia, the elements between the muscle-fibres or 
bundles, the nerve-sheaths, &c. True parenchymatous tissue with walled 
cells, without intercellular substance and extraneous cell-fibres, reaches 
its greatest quantitative development in Carinella and Cerebratulus , and is 
least in Stichostemma ; it is absent on the lateral blood-vessels in Lineus 
and the Metanemertini, and in the head and oesophageal regions in all 
the species. It probably functions as a layer for the mutual transfusion 
of the rhynchocoelomic and blood fluids. The cells of the intracapsular 
connective tissue of the nervous system are, in all species except perhaps 
Stichostemma, divisible into two categories : — (a) those between the outer 
and inner neurilemma ; and (b) those around and within the fibrous core. 
A noticeable body-cavity is undoubtedly present in Carinella and 
Cerebratulus , and in a more reduced state in Lineus gesserensis, Amphi - 
porus, and Stichostemma. It consists of a slit between the intestine and 
proboscis-sheath, and the body-wall ; in Cerebratulus it is a very evident 
cavity, with both fixed and free mesenchyme cells. There is none in 
Metanemertini. 
The gonadal membrane is apparently always a product of the con- 
nective tissue cells, with dense intercellular substance ; the genital cells 
are either derivatives of cells of this tissue (in Lineus and the Metanemer- 
tini), or of mesenchyme cells (in Carinella and perhaps Cerebratulus). 
In the adult Nemertean, amitotic division is seen in the mesenchyme- 
cells ; but no cell-divisions occur in the other connective tissues, except 
those true mitotic divisions (in the tissue with intercellular substance)- 
which give rise to the genital cells. 
The relationships of the various Nemertean connective tissues may be- 
illustrated graphically as follows : — 
I. Parenchyma. II. Mesenchyme. 
1. Intracapsular ] 
connective U A 
tissue I 
B. Connective tissue 
with intercellular 
substance. 
2. Interstitial I 
tissue of body ><- 
epithelium ) 
3. Pigment-tissue 
of body- wall 
(Lineus). 
* Zool. Jahrb. Abtli. Anat., x. (1897) pp. 1-46 (4 pis.). 
