SCIENTIFIC SUMMARY. 
445 
the insects, and say that from the facts ascertained they are disposed to 
adopt Mr. McLachlan’s opinion, that Prosopistoma is an Ephemerid, probably 
adapted permanently to an aquatic life. 
Abnormal Dentition in a Tiger. — Mr. Lydekker describes and figures 
(“ Journ. Asiatic Soc.,” Bengal, 1878) the lower jaw of a tiger from Burma, 
in which a third premolar is developed on one side. The specimen is inte- 
resting, because in the extinct feline genus Pseudcelurus the third premolar 
is always present. Pseudcelurus was founded on a Miocene fossil from 
Sansan, in France, and other species have been described from the Pliocene 
of Nebraska, and from the Sevaliks. 
Entoniscus in France . — Among the parasitic crustaceans described by Dr. 
Fritz Muller perhaps none was more curious than that to which he gave the 
name of Entoniscus , a true isopod crustacean, the female of which, after a 
short free life, took up its abode in the abdomen of a crab, and became 
■converted into a great sac branching about among the viscera of its host. 
Hitherto these parasites have been only known to occur on the Brazilian 
coast, where they were studied by the distinguished naturalist above-men- 
tioned ; but M. Giard has now discovered two species on the coast of 
France, one of which, however, he believes to have been seen long since by 
Cavolini. The commonest of the two species, which M. Giard names 
Entoniscus Cavolinii, is found under the carapace of Grapsus marmoratus f 
Fab., an abundant species on the rocks at Pouliguen, Loire-Inferieure ; and 
the parasite is so numerous that out of thirty crabs one will usually be found 
to bear it. The second species is much less common, occurring only in 
about 1 per cent, of the crabs on which it is parasitic, the Velvet Crab 
( Portunus puber ), a British species. To this M. Giard gives the name of 
Entoniscus Moniezii. It is unnecessary here to indicate the characters of the 
species, but some remarks of M. Giard ’s upon the active embryo of Entoniscus 
Cavolinii are of considerable interest. He finds that, besides the lateral eyes, 
which are double and correspond to the eyes of the normal isopods, the embryo 
possesses a median eye, composed of two contiguous crystallines, with pigment 
and optic nerves. This he regards as the Nauplian eye, which has persisted, 
retaining a structure such as is met with in many copepods, and which 
afterwards disappears with the secondary eyes during the retrograde meta- 
morphosis of the female Entoniscus. This fact is of special importance, if it 
is a real trace of the occurrence of a Nauplius stage in the development of 
this curious isopod. ( Comptes rendus , September 2, 1878.) 
Cit'cidation in Insects. — Mr. S. H. Scudder has read before the Boston 
Society of Natural History (Proc. vol. xix. part 1), some remarks upon the 
circulation of insects, a subject upon which, as he justly says, many contradic- 
tory views have been held. He says the juices of the digested food appear 
to pass directly through the thin walls of the alimentary canal into the 
general cavity of the body ; from this they are pumped into the hinder 
extremity of the pulsatory dorsal vessel, by its alternate contractions and 
dilatations, while in many cases portions also appear to enter the sides of the 
vessel just in advance of the valves which aid the pulsating action by allow- 
ing a free passage to the fluid only in a forward direction. In the larval 
state the walls of the pseudocardium are often so slight as to be scarcely 
perceptible ; but they are distinct in the imago, and as the vessel contracts 
