5132 
SUMMARY OF CURRENT RESEARCHES RELATING- TO 
of the stigmata more or less along the whole body in Arachnida indicates 
the adherence of the Arachnids to the Tracheate series. 
Jaworowski allows himself considerable range of speculation. Not 
only does he derive the respiratory organs of Limulns (supposed to be 
originally terrestrial) from the Arachnid type, that is from modified 
tracheae, but he applies a similar theory to the Crustacea. The divisions 
of the limb are explained as modifications of a respiratory lamella ; four 
reasons are urged against deriving the Crustacean limb from the Annelid 
parapodium, and five in favour of deriving the gills from the lamellae of 
so-called lungs. In short the Crustacea passed through a Prototracheate 
stage. But as the author says, these “Ansichten sind vielleicht zu 
kiihn.” 
Eye of Phalangiidae.* — Herr F. Purcell finds two types, differing in 
the structure of the rhabdome — the Leiobunum- type and the Acantho- 
lophus- type, and describes these in detail. We can only cite a few out- 
standing results. 
One of the most important characteristics of the retina is the constant 
arrangement of its elements in groups (retinulae), each of four cells, and 
the union of the optic rods of these four cells into a rhabdome, which, 
though single, is composed of four rhabdomeres. There are no pigment 
or other cells between the retinulae. 
In all the species examined the rhabdome consists of two chemically 
different parts. The one part includes the whole central rhabdomere 
and, in the Acantholophus-growp , the distal portion of the peripheral 
rhabdomeres ; the other part includes in the Leiobunum group the whole 
of j the peripheral rhabdomeres, in the Acantholophus group only the 
proximal part of the same. 
The eyes of Phalangiidae. are three-layered inverse eyes of ectodermic 
origin. The anterior median eyes of spiders, the eyes of Phalangiidae, 
the median eyes of scorpions, and at any rate the median eyes of the 
king-crab form a series of homologous structures, characterized by an 
inverted retina with retinulae or at least rhabdomeres. As a chief result 
of his investigation the author claims to have definitely proved that a 
retina composed of retinulae or of a modification of these occurs in 
higher Arachnid orders — Phalangiidae and Spiders. 
Irish Pycnogonida.t — Mr. G. H. Carpenter has a short report on 
the Pycnogonids collected in deep water off the Irish coasts and on 
those in the Dublin Museum. The only list of Irish Pycnogonida is 
that of W. Thompson, who enumerated nine species ; of these Mr. 
Carpenter can confirm only three or four ; the remaining five in the 
list before us are now for the first time recorded as Irish. The widely 
distributed Anoplodactylus petiolatus is represented by a single female. 
The suggestion that PJioxichilus is descended from Nymphon-\ike 
ancestors is accepted, and further evidence brought to confirm it. 
Systematic Position of Trilobites.t — Mr. H. M. Bernard thinks that 
it is now possible to fix with great probability the zoological position 
of Trilobites. He considers that the bending round ventrally of the 
* Zeitschr. f. wiss. Zool., lviii. (1894) pp. 1-53 (2 pis.), 
t Sci. Proc. Roy. Dublin Soc., viii. (1893) pp. 195-205 (1 pi.), 
t Quart. Journ. Geol. Soc., 1. (1894) pp. 411-32 (17 figs.). 
