448 
SUMMARY OF CURRENT RESEAKCHES RELATING TO 
among the larger Arachnida from not possessing them. They have 
probably been missed from the alteration in position, for they have been 
shifted over the edge of the dorsal surface on to the lateral so that they 
look downwards and forwards. Their irregular form and, perhaps, 
their position indicate that they are undergoing atrophy ; they have 
lost all traces of a lens, and as the chitin is thinned away over them, we 
have merely minute eyes that are little more than plugs of pigment in 
deep cliitinous pits. 
Endosternite of Arachnids.* — Mr. W. Schimkewitsch refers to 
Mr. Bernard’s recent attempt to liomologize the apodemes of Galeodes 
with the endosternite of other Arachnids,' f and points out that treatment 
of Androctonus bicolor with caustic potash and a series of transverse 
sections of a young Scorpion will show that the apodemes of Galeodes 
are entirely represented by the less developed apodemes of the 
Scorpion. 
Parthenogenesis of Sarcoptidse.f — M. E. Trouessart finds distinct 
parthenogenesis in Syringobia chelopus Trt. and Neum., a Sarcoptid of 
the sub-family Analgesinse, and a parasite on the feathers of the wader 
Tot anus calidris. 
At the time of the annual moult, which precedes the southward 
migration of the bird, a few nymph -individuals of Syringobia enter the 
young feathers by the superior umbilicus. If there are individuals of 
both sexes, the colony illustrates the normal series ; but if all be female, 
the nymphs increase in size and become parthenogenetic. In the warm 
country the young forms issue from the quill, and normal colonies live 
on the barbs as usual. On the approach of the spring migration north- 
ward, the young enter the quill by the superior umbilicus, and form both 
normal and parthenogenetic colonies, while the external colonies dis- 
appear. Thus the parthenogenesis is determined by two factors — 
hibernation in the quill, and the absence of males in a given colony. 
Structures resembling Dermal Bones in Limulus.§ — Dr. W. Patten 
finds, under the external chitinous covering of the body of Limulus , 
remarkable bone-like structures ; they consist of a network of chitinous 
bars with irregular spaces through which blood-vessels and nerves ramify. 
In some, probably very old, individuals, the axis of each bar is densely 
crowded with spindle-shaped cavities or lacunse ; their long axes are 
parallel to the long axis of the bar, and at times many may be seen to 
be connected at one end with a very fine tubule, or canaliculus, which 
runs radially towards the periphery. The lacunae arise on enlargements 
of the distal ends of these canaliculi. 
The author insists on the remarkable character of this dermal struc- 
ture, quite unlike anything known in any other Invertebrate ; though 
he ventures to predict that similar structures will be found in Trilobites 
and Merostoma, when they are properly investigated. Indeed, the only 
animals known to show such an exoskeleton as Limulus are some of the 
fossil fishes which are called Cephalaspidse, and the most striking resem- 
blance is shown by Pterasjois. 
* Zool. Anzeig., xvii. (1894) pp. 127 and 8. t See ante, p. 192. 
t Comptes Rendus, cxviii. (1894) pp. 1218-20. 
§ Anat. Anzeig., ix. (1894) pp. 429-38 (4 figs.). 
