ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 997 



divide faster than the rest, and that area becomes a little depressed. 

 "When the cells multiply most rapidly, invaginatiou occurs, and 

 a gastrula is formed, the cavity of which soon becomes comparatively 

 deep. Later on, the blastopore closes ; somewhat in front of it, a 

 fresh invagination gives rise to the permanent anus. On the opposite 

 side we get the first indications of the cephalic lobes which gradually 

 travel upwards (or, morphologically, backwards). The order of 

 formation of the parts of the embryo is — abdomen, mandible, 

 cephalic lobes, carapace, antennae. 



The stomodceum is, like the proctodoeum, a formation apparently 

 independent of the blastopore, and is at first a narrow blind tube ; 

 later on, other appendages appear ; the heart seems to be mesodermic 

 in origin. 



The embryo, when just hatched, measures about 3:j; mm. in length ; 

 the broad carajiace is produced anteriorly into a rostrum, at the base 

 of which is the simple eye ; the compound eyes are large, and sup- 

 ported on very short stalks, the telson is still united with the last 

 segment. Four pairs of thoracic appendages are already formed, 

 but no trace of abdominal appendages is to be detected. In its later 

 changes the embryo agrees largely with Palaemonites, as described 

 by Faxon. 



Sense-organs of Calanidae.* — Dr. O. E. Imhof has some notes 

 upon the antennary olfactory organs of the genera Heterocope and 

 Diaptomus. 



These appear to have been discovered in Heterocope by Gruber ; 

 in Diaptomus they exist in all the species examined, and have a 

 characteristic distribution which is the same in all the species, and 

 may, perhaps, serve as additional definition of the genus. The form of 

 the organs in Diaptomus is a little less complicated than in Heterocope ; 

 they resemble very closely the corresponding organs of Pontella 

 described by Claus. 



Polymorphism in the Amphipoda-f — Mr. C. Chilton states that 

 the Amphipod Microdeuteropus maculatus of Thomson, which is the 

 same as Aora typica of Kroyer, has three forms of the male and only 

 one of the female. The males all difier from the female in having 

 the meros of the first gnathopod produced into a long spine reaching 

 to the end of the carpus ; in the first form of male [Aora typica K.) 

 the carpus is longer but no broader than the propodos, and the bases 

 has a tooth projecting forwards on the anterior margin ; in the second 

 (Microdeuteropus maculatus $ Chilton) the carpus is larger and 

 broader than the propodos, and the meros has a small tuft of sctre on 

 the posterior margin ; in the third (ilf. mortoni Haswcll) the carpus is 

 longer and broader than the propodos ; the meros is hollowed 

 anteriorly, and has each lateral margin densely fringed with sette, 

 while the dactylos is as long as the i^ropodos, and has two or three 

 tufts of sctfc on its concave border. 



* Zool. Anzclg., viii. (1885) pp. 353-C. 

 t Ann. nnd Mag. Nat, Hist., xvi. (188.5) pp. 3C8 70 (1 pi.). 

 S^T. 2.— Vol.. V. 3 T 



