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SUMMARY OF CURRENT RESEARCHES RELATING TO 
open groove, which in form rocalls that of the medullary groove of 
higher Vertebrates. 
The rest of the ectoderm, in stained specimens, breaks up into three 
differently coloured zones; in the outermost are a large number of 
nematocysts and of unicellular glands, while in the median the nuclei are 
very closely packed. Nervous elements could not be made out, but 
there is no doubt that they are among the various constituents of the 
ectoderm. The nuclei are larger than those of the flagellate cells, and 
show well-marked dots, the most apparent of which is, perhaps, the 
nucleolus. Some of the nematocysts are small, and have the form of 
cylinders, within which is a thread which describes an extremely 
regular spiral ; others, which are larger, ovoid, rarer, and more deeply 
seated, have an irregularly arranged spiral. There are also two kinds 
of glandular cells ; some are coarsely but uniformly granular, while others 
have clear contents and a homogeneous or reticulated appearance. 
The mesenchymatous layer is remarkably thick, and contains a very 
large number of cellular elements. Some of the cells are large, and 
their protoplasm acts energetically on the colouring material ; they may 
be rounded, fusiform, or stellate in shape. Others are much smaller 
and have always very fine and colourless prolongations. The new 
form is remarkable among Actinian larvae for the constitution of its 
fundamental lamella, which is not simple, but is a well-characterized 
cellular tissue, while the differentiated cellular strata of endoderm and 
ectoderm, which are in immediate contact with it, have almost the 
appearance of the layer of osteoblasts of bony tissue, or the odonto- 
blasts of teeth. 
The coelenteric cavity has about the middle of the long axis of the 
body the appearance of a transverse cleft ; it is broken up at its 
periphery by three pairs of macrosepts, which have on their free edge a 
mesenteric swelling, into six spaces, the largest of which, in the trans- 
verse direction, is the medioventral. There are also six microsepts, 
the three pairs of which are unequally developed. The endodermal 
layer which lines the two surfaces of the mesenchymatous lamella of the 
mesenteries is delicate and formed of cubical cells, which are here and 
there replaced by fusiform elements. The mesenteric swellings exhibit 
no tendency to form convolutions ; all the cells that compose them are 
conical and radiate in all directions around the slightly swollen 
extremity of the mesenchymatous layer. 
In each macrosept a layer of longitudinal muscular fibrils may be 
seen in the form of a row of shining grains. The microsepts differ from 
the macrosepts in having their very short mesenchymatous layer almost 
reduced to the terminal enlargement of the macrosepts, in the delicacy 
of their endodermal layer, and the absence of the mesenteric swelling. 
After describing the appearances of transverse sections taken at 
different levels, Prof. Van Beneden proceeds to point out the resem- 
blances and differences between this new larva and that of Semper ; the 
former are the general form of the body charaeteiized by its considerable 
elongation, the existence of six well-developed sarcosepts, the total 
absence of any trace of tentacles around the mouth, and above all the 
presence of the median vibratile fringe ; the latter are the cylindrical 
shape of one larva and the pyriform of the other, the difference in the 
