VAN DEE HCEVEN’s ZOOLOGY. 
87 
actions of the Society of Naturalists of Halle/’ vol. iv. part 1. At the 
end of the Annulata we find the genus Sagitta. Upon the elaborate 
memoir in the last-mentioned Transactions by Gegenbaur, we learn that 
in the development of the ova the most noticeable points are,—the di¬ 
vision of the yolk produces long pyramidal cells, having their base at 
the surface and their apex towards the centre, which retain this form 
even after the formation of the embryo has commenced; the origin of 
the intestinal canal is contemporaneous with the division of the yolk, and 
it appears at first as a central cavity of the yolk, the communication with 
the exterior being established at a later period; the development from 
the egg is completed without any metamorphosis, not even cilia being 
produced on the surface of the embryo: hence the type of development is 
totally different from that of the Mollusca, the embryo being formed 
without metamorphosis, without a velum, or even the temporary presence 
of cilia. This last circumstance distinguishes it from the Annelides and 
Platodes, but points to the analogy with the Nematodes, with which 
also the mode of development agrees best throughout, except as regards 
the singular form of the segmentation cells and the first formation of the 
intestinal cavity. These peculiarities tend to confirm the views of the 
first observer, Slabber, who placed Sagitta among the worms, but as a 
peculiar group—dart-worms, which Gegenbaur would intercalate be¬ 
tween the Nematodes and Annelides. This paper is illustrated with a 
nicely executed plate, and is a most valuable memoir, it being only by 
the careful tracing out of the development of such doubtful genera as 
Sagitta that we can ever hope to arrive at their natural position among 
the families. 
To come to the Annulosa proper, we first arrive at the Insecta. We 
do not at all agree with the division adopted by Van der Hoeven : he 
makes twelve orders—Myriapoda, Thysanura, Parasitica, Suctoria, Strep- 
siptera, Diptera, Hymenoptera, Lepidoptera, Neuroptera, Hemiptera, 
Orthoptera, and Coleoptera. How much better and simpler would it 
have been to have separated the first order altogether from true inserts, 
and then to divide Insecta into five orders. In the preface to the second 
volume we are informed that the author does not insist on the distinct¬ 
ness of the fifth order, agreeing, with modem authors, to place it among 
the Coleoptera. It would have been equally well if the translator had 
referred the Suctoria to the Diptera (see Haliday’s most important pa¬ 
per on this subject, “ Proceedings of the Dublin University Zoological 
Botanical Association,” 1856); the Thysanura and Orthoptera to the 
Neuroptera; the Parasitica to the Hemiptera. On the Insecta the 
author does not appear to be up to the English literature; with the ex¬ 
ception of Westwood, he hardly mentions a single name. We may, 
perhaps, add a paper by Schiodte on the structure of the thorax in 
insects as a ground of classification, in the “ Proceedings of the Danish 
Boyal Society” for 1855. So many important papers have lately ap¬ 
peared in the Proceedings of the various British and Continental Societies 
that we cannot afford room even to allude to them. 
In the next class, that of the Arachnida, is placed the order Poly go- 
