ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
607 
aggregates observed by Uhde in the setigerous regions of segments 
9-11, 26 and 29 are connected with nerves which arise from the 
abdominal ganglia. In AllolobopJiora foetida the glands of the clitellum 
are sometimes not confined to the hypodermal layer, but traverse the 
circular and longitudinal layers of muscles. The innermost, third, layer 
of the membrane of the nervous system is connective and not cuticular. 
The suboesophageal ganglion of Lumbricus terrestris gives off eight pairs 
of nerves, and not seven, as stated by Friedliinder. The contents of the 
nerve-canals consist of fibres which are imbedded in a plasmatic mass. 
The author’s account of the histology of the stomach does not agree with 
that of Claparede ; he finds the gastric cavity lined by epithelial cells, 
above which there is a layer of cells, which in form resemble those of 
the coelom; they are succeeded by the circular and longitudinal layers 
of muscles. On the abdominal surface the circular muscles run parallel 
to the abdominal wall of the stomach, while at the sides they are directed 
obliquely to the axis of the body ; the fibrils of the circular muscles are 
longitudinally striated, and in isolated filaments nuclei may sometimes 
be found. The longitudinal muscles are in the form of special bands 
which vary in form in cross section. 
In the region of the typhlosole and the cylindrical cells which line the 
enteric cavity cells are sometimes found which, in form, closely resemble 
those of the coelom ; similar cells are also found in the muscular layers 
of the enteron ; all intermediate stages are found between these and the 
chloragogen cells. The various statements which have been made as to 
the number of heart-like vascular loops in various species of earthworms 
are probably due to the age of the worm and the time of year when the 
investigation was made ; in winter these loops are narrower in diameter 
than they are in summer. Every heart has not the form of a string of 
pearls, but of a curved tube narrowed at either end, where it opens into 
the dorsal and abdominal vessels. 
Development of Germinal Layers of Tubicolous Gephyrea.* — M. L. 
Roule has studied at Cette the development of the germinal layers of 
Phoronis Sabatieri. The fertilized egg undergoes very regular segmenta- 
tion ; the young morula, composed of thirty-two blastomeres, has no 
central cavity, and the divisions of the cells are effected in all directions. 
Most, however, are radial in direction and a blastoccel appears which 
gradually increases in size. The young spherical blastula takes on an 
oval and then a discoidal form. When it becomes a disc flattened on 
each surface it becomes depressed in the centre. The blastopore of this 
gastrula soon becomes excentric in position, and the body becomes divided 
into a preoral and a postoral portion. 
In the narrow blastocoel there may soon be seen a few thick cells 
which arise from the meso-endoblast and form a primary mesenchym. 
Later on, the archenteron becomes pierced by a second orifice which 
forms the anus of the Actinotrocha , while the blastopore becomes the 
mouth. The ectoblastic cells at the tip of the preoral region elongate 
considerably and so produce a small cephalic plate. The initial meso- 
blast-cells segment and give rise to some mesenchymatous cells which 
form the mesoblastic stripes. 
* (Joinples Reudus, ex. (1890) pp. 1H7-9. 
