ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
629 
ally narrows and is shunted forwards. In the anterior third of the body 
it closes. Thereafter the endodermic process forms the caecum. 
The head-groove arises as a group of much vacuolated ciliated cells, 
which sink in a little around a cavity. The head-gland arises dorsally 
near the groove as a slightly insunk plate, the anterior part of which 
forms a small invagination. 
The first hint of the proboscis is in a few much elongated cells, 
which are invaginated, and divide longitudinally. (Esophagus and 
rectum arise as invaginations. The brain appears as two pairs of 
I* ectodermic thickenings, which form the dorsal and ventral lobes. In 
connection with the latter, the longitudinal nerves arise as two ecto- 
dermic strands. The dorsal nerve arises separately but similarly. The 
cerebral organs arise as two thickenings of the ectoderm, which are 
subsequently invaginated to form ciliated cavities. 
Epithelium of Tapeworms and Flukes.* — Mr. A. E. Shipley calls 
attention to a recent work on the histology of these two groups of 
parasites. Prof. Blochmann has pointed out that if they have no 
external epithelium, we must invent a new name for the cuticle, since 
it is of the essence of cuticle that it should be formed from the free ends 
of epithelial cells. The external glands which are common in flukes, 
and also occur in tapeworms, are as a rule, produced by the modification 
of some of the cells of an epithelial layer. Lastly, absorption, which 
takes place all over the body of a tapeworm, is usually in other animals 
effected by an epithelium. It is probable, therefore, that an epithelium 
exists in these parasites. 
According to this writer, the external epithelium has, to some extent 
sunk into the parenchyma, so that we do not find a sheet of contiguous 
epithelial cells on the inner side of the cuticle. The lateral separation 
of the epithelial cells is caused by the intrusion of the parenchyma. 
This parenchyma, like other connective tissues, consists of cells and a 
ground-substance ; the cells are very richly branched, and stretch 
through the body in all directions ; they unite with those of other cells 
so that the parenchyma cells are able to play a large part in the 
nutrition of the parasite. 
Nervous and Muscular Systems of Ligula.t — Dr. M. Liihe notes 
the close resemblance between the musculature of Ligula and that of 
Boihriocephalus ; both have subcuticular, external, and internal longi- 
tudinal muscles, but the distinction between the subcuticular and the 
external longitudinal muscles is by no means sharp. As Niemiec pointed 
out, there are in Ligula numerous accessory longitudinal nerves between 
the external and internal longitudinal muscles. These are all connected 
by commissures running parallel to the surface, and the two main nerves 
also give off branches to this commissural plexus. Thus the system is 
more complicated and more like that of Trematodes than was supposed. 
Apart from those in the scolex, commissures have been previously re- 
corded in Moniezia expansa (by Koehler), M. planissima (by Tower), and 
in Anoplocephala magna (by Scheibel). Their discovery in Ligula sug- 
gests the probability that they will soon be found in others. 
2 x 
1896 
* Science Progress, i. (1896) pp. 78-81 (1 fig.), 
t Zool. Anzeig., xix. (1896) pp. 383-4. 
