Arachn, 1 
ARACHNIDA. 
13Y 
The Rev. 0. P. Cambridge, M.A., C.M.Z.S., &c. 
(Assisted by P. M. Campbell, P.L.S., &c.) 
List op General Publications. 
Balfour, F. Development of the Araneina. Q. J. Micr. Sci. xx. 
pp. 1G7-189. 
Contains a very valuable account of the development of the ovum in 
Agelend lahyrinthica, in all its stages. The results point to the affinity of 
Arachnids being more with the Tracheata than with the Crustacea 
(Branchiata) ; and that the falces (chelicerae) are true mandibles, not 
antennae, seems pretty certain. [C/. “ Studies from the Morphological 
Laboratory in the University of Oambridgo,” 1880, pp. 83-lOG, pis. viii.-x., 
where the present paper is reprinted.] 
. Comparative Embryology, London ; 1880. 
Yol. i. pp. 357-379, treats on Araclinida. The special history of each 
group as yet worked out is dealt with : Scorpionidm, p. 357 ; Pseudo-, 
scorpionidoi^ p. 359 ; Phalangidce (of which nothing of the early stages 
appears to be known), and Araneina, p. 3G1. The treatment of this last 
Order is as nearly as possible identical with that in the work above 
recorded (Q. J. Micr. Sci. xx.). The subjects are Pholcus, Epeira, 
Lycosa, Clubiona, Tegenaria, and Agelena. The history of the germinal 
layers in this Order is given, pp. 369-375. The conversion of these 
layers into the various organs agrees closely with that in Scorpions. 
“ Summary and general conclusions ” are given, pp. 376 & 377. 
It is stated in these that Scorpions and Spiders agree more nearly 
in their embryonic forms than Scorpions and Chelifers, which is 
probably because of the very early stage at which the latter are 
hatched. The larvae of the Acarina are much modified larval forms, but 
it is not easy to assign a meaning to the hexapodous stage generally 
passed through. The chelicerao (falces) are not homologous with the 
antennae of lusecta, being always developed on the post-oral segments, 
and corresponding to the mandibles of Insects. Arachnid appendages 
are, therefore, much more primitive in their present condition than those 
1880. [vOL. XVII.] B 20 
