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REPORT ON ZOOLOGY, MDCCCXLII : 
layers, united by animal matter, and laid above one another, but which 
can be separated by maceration in caustic alkali. The alimentary canal 
is simple, without caecum ; it also wants salivary glands and liver. The 
vascular system, in grown individuals, is not easily examined. The 
organs of respiration appear chiefly to be the membranous feet, which 
have a great similarity to those of the seventh or ninth pairs of Apus. 
The males are distinguished by a pair of peculiarly-formed grasping- 
feet, which are situated before the branchial members ; besides these, no 
male organs could be found. The ovaries of the female resemble those 
of Apus ; but no external passages could be found. The author con- 
siders, as the brain, a flattened part, situated under the eyes, which 
sends up a thin process towards them, while the optic nerves pass 
ofi* from the posterior extremity. The oesophageal ring and ganglionic 
chain could not be perceived. The Isaura always swims with the back 
upwards, not by means of the branchial membranes, but only by their 
ramose rudder-like members, which the author calls antennae. Con- 
fervae were found in the intestines as nourishment. Copulation takes 
place, as the author had abundant opportunity of observing, by the male 
grasping, with his claws, the under margin of the shell of the female, 
and penetrating, with the end of his body, between the two shells. 
How the seminal fluid arrives at the egg, the author has not observed. 
The fertility is very great. He counted, in one female, a thousand eggs. 
The development of the young agrees, in a great degree, with those of 
Branchipus and Artemia, as they come out of the egg. They have two 
pair of large rudder-shaped membranes, the second of which afterwards 
shrinks, as the branchial members develop themselves. At first neither 
blood nor circulation can be seen ; after six days, globules of blood, and 
dorsal vessels, show themselves ; and the beginning of the shell appears, 
like a horizontal membrane, upon the back. Two days afterwards, the 
shell becomes perpendicular, and encloses the little animal. The bran- 
chial members are then found so far developed, that the second pair of 
rudder-shaped members have disappeared ; while, on the contrary, the 
first pair have attained a greater degree of development. 
Waga (Ann. d. 1. Soc. Ent. d. Er. xi. p. 261, t. 11, f. 1-4) has made 
known a new species, Branchipus torvicornis, which is remarkable for 
the great hook-formed organs of the male, which are twisted, and send 
otf several branches. He found it in the neighbourhood of Warsaw, 
in a deep dirty puddle. 
SIPHONOSTOMA. 
H. D. Goodsir (James. Edin. New Philos. Journ. xxxiii. p. 178 ; Ann. d. 
Sc, Nat. xviii. p. 188) has given some observations on the development of 
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