490 SUMMARY OF CURRENT RESEARCHES RELATING TO 
itself under a load of debris which it holds on its hack by its feet. The 
most strikingly conspicuous creature on the coral reefs is the formi- 
dable Diadema setosum. The Asterida were the smallest in number of 
individuals. Differences of coloration in the sexes of a species of 
Ophiothrix were observed. 
New Genus of Echinoids.* — Mr. J. W. Gregory defines a new 
genus Archseopneustes, in which he places the Paldeopneustes hystrix of A. 
Agassiz, a new fossil species from Barbadoes, which he calls A. abruptus, 
and Asterostoma cubense, of Cotteau. In these three species the petals 
are continued to the margin, and the mouth is very excentric anteriorly, 
whereas in Palseopneustes the petals are short and closed, and the mouth 
is more central. The first genus has, further, an elliptical and conical 
test, and the second one that is more evenly rounded. 
An abnormal Cucumaria.| — Prof. H. Ludwig describes what looks 
like a two-headed specimen of Cucumaria planci. The supernumerary 
anterior outgrowth, which lay between the two left ambulacra, included 
a duplication of the parietal organs — water- vascular vessels, nerves, 
blood-vessels, and muscles, but did not include any repetition of the gut. 
Ccelenterata. 
East African Coral Reefs. £ — Dr. A. Ortmann briefly describes these 
as true fringing reefs, associated with “negative shore displacement,” 
i. e. elevation of the coast. To the south of the district visited (from 
Zanzibar to Mikindani), where deep water occurs close to the shore, the 
reefs are narrow, in other parts the shallow water has admitted of broad, 
flat reefs. No true barrier-reefs or atolls were seen. These, he believes, 
can arise only in regions with a positive shore displacement, or in rare 
cases in stationary regions. He holds to the “ Darwin-Dana ” theory, 
and rejects Guppy’s conclusions. The atolls which J. Walther described 
in the Red Sea are not true atolls. Ortmann observed that corals 
( Porites , Goniastrsea, Goeloria , Tubipora) may survive low- tide exposure 
for hours. He also found some living on a loose substratum of sand 
and gravel held together by sea-grass. 
Cassiopea xamachana.§— Mr. R. P. Bigelow gives an account of 
this new species from Jamaica. It is allied to G. andromeda Esch. and 
C. polypoides Keller. An important part in reproduction is played by 
the production of buds by the Scyphistoma. The bud is set free as a 
ciliated, hollow, planula-like body consisting of a layer of ectoderm and 
of endoderm, with a thick supporting layer between, in which the four 
septal muscles are imbedded. After the formation of a mouth the larva 
becomes fixed and developes into a Scyphistoma. Strobilization is 
monodiscous. More detailed accounts follow. 
Development of Marginal Sense-organs of a Rhizostomatons 
Medusa.il — Mr. R. P. Bigelow finds that Goette’s view, which he was 
inclined to adopt, that the rhopalia are formed as evaginations from the 
under surface of the marginal part of the umbrella, entirely independently 
* Quart. Journ. Geol. Soc., xlviii. (1892) pp. 163-9 (1 p].). 
f Zeitschr. f. Wiss. Zool., liii. (Suppl.) pp. 21-30 (1 pi.), 
j Zool. Anzeig., xv. (1892) pp. 18-20. § Tom. cit., pp. 212-4. 
|| John Hopkins Univ. Circ., xi. (1892) pp. 84-5. 
