ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
123 
colourless elliptical ova ; tlie larvm and the nymphs. A detailed account 
with figures is forthcoming. 
Pseudo-Larval Copulation of some Sarcoptidse.* * * § — M. S. Jourdan 
has made a study of three forms of plumicolous Sarcoptids, often found 
on the domestic pigeon. In these forms the male copulates with an 
octopod larva, which has no sexual apparatus ; this paradoxical arrange- 
ment cannot he understood till it is seen that beneath the skin of the 
larva a perfect female is being formed, and it is into this that the fer- 
tilising fluid passes ; hence the suggested term “ pseudo-larval.” 
Halacarina of the ‘ Caudan ’ Expedition^ — Dr. E. Trouessart has 
a full and interesting report on the marine A carina collected by Prof. 
Koehler in the Bay of Biscay ; they are the first of their kind known 
from great depths, and these latter extended from 180 to 1410 metres. 
They were chiefly found attached to Amphihelia prolifera and Soleno - 
smilia varicibilis ; when these corals fail the halacarine fauna becomes 
excessively poor. As a fact, examples were dredged at five stations 
only, and representatives of new species were out of all proportion more 
numerous than those of old ; by far the most abundant was Halacarus 
abyssorum sp. n. ; there is a single representative of a new genus, 
Atelopsalis tricuspis sp. n. 
The halacarine fauna of great depths is remarkable for the complete 
absence of phytophagous types, the scarcity of predacious or carnivorous 
forms, the frequency of types with a feeble rostrum and styliform palps, 
the thinning of the chitinous integument, and the variations in the 
development of the eyes. 
Pycnogonida of the ‘Caudan’ Expedition.^ — M. M. Caullery re- 
ports on the three Pycnogonids collected by Prof. Koehler in the Bay 
of Biscay. One of these, Paranymphon spinosum , is a new genus and 
species, but it is to be observed that the sole distinguishing generic 
character given is the presence of six joints to the palp instead of five, 
as in Nymphon. 
g. Crustacea. 
Functions of certain Diagnostic Characters of Decapod Crus- 
tacea^ — Mr. W. Garstang discusses the value of certain characters used 
by systematists to distinguish species and genera. For example, the 
frontal area of Crabs is frequently either 3- or 5-toothed, that is, either 
2- or 4-notched. This is an arrangement by which the antennce 
and antennules, which are organs of great importance, are specially 
protected against injury. In sand-burrowing species the denticulated 
margins have the function of sieves. 
It is not, says the author, generally known that a crab’s chelipeds are 
in many cases important agents in the process of respiration ; this is 
explained and illustrated. 
It appears, to conclude, that many of the specific and generic charac- 
teristics of Crustacea, which have been hitherto regarded as features of 
trivial significance, are really of primary importance to their possessors. 
* Comptes Rendus, cxxiv. (1897) pp. 209 and 10. 
f Resultats Scient. de la Campagne du ‘Caudan,* fasc. ii. (1896) pp. 325-53 
(3 pis.). + Tom. cit., pp. 361-4 (1 pi.). 
§ Rep. Brit. Ass., 1896, 2 pp. (sep. copy). 
