No. 404.] REVIEWS OF RECENT LITERATURE. 677 
Gobius, Benthrophilus, and Syngnalhus were obtained, together with 
numerous Crustacea, many Mollusca, a few worms, and some alga. 
A study of the genera Hygroceleuthus and Dolichopus has led 
Melander and Brues (Biol. Buil., Vol. I, p. 123) to place all flies 
belonging to the former genus under Dolichopus, though the species 
thus transferred form a natural group of less than generic value. In 
their revision of this genus the authors describe thirteen new species. 
The structures which have been described by previous writers 
as the rudimentary dental ridges in embryo birds have been reinves- 
tigated by H. D. Tjeenk Willink (Zz4seAr. d. Ned. Dierk. Ver. (2), 
Bd. VI (1900), pp. 243-254, Taf. XI). These structures are easily 
identifiable in many species of birds, but are too well developed to 
be called rudimentary. If they are the remains of dental ridges, 
which the author believes is by no means certain, they have most 
assuredly assumed secondary functions and contribute materially to 
the formation of the horny bill. This function in itself is a sufficient 
explanation of their presence, without assuming that they are the 
remains of dental ridges. 
Vanhöffen (Zool. Anzeiger, Bd. XXIII (1900), pp. 277-279) has 
investigated the finer structure of three genera of deep-sea medusa, 
Atolla, Periphylla, and Periphyllopsis, on material all of which was 
collected from a greater depth than 600 meters. Both Haeckel and 
Maas believed that the deep-sea medusz possessed, in addition to 
statocysts, eyes of a simple type. Vanhöffen finds no evidence of 
eyes in the material studied by him and believes that Haeckel mis- 
took pigmented entoderm for eyes, and that Maas was in error 
because of imperfectly preserved specimens. 
Bittacomorpha clavipes Fabr., a near relative of the crane flies, is 
characterized by having enormously swollen metatarsi on all its legs. 
Brues (Biol. Buil., Vol. I (1900), pp. 155-160) has found that an 
enlarged tracheal tube occupies almost the entire cavity of the 
swollen metatarsus. As this insect flies poorly, the author believes 
that the balloon-like enlargements of its metatarsi enable it to be 
wafted easily by currents of air. The coloration of these parts gives 
the animal, when suspended in air, a striking resemblance to drifting 
thistle seeds. 
The third number of Vol. I of the Biological Bulletin contains the 
following papers : “ The Early Cleavage and Formation of the Meso- 
derm of Serpulorbis squamigerus Carpenter," by S. J. Holmes ; * New 
