ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 483 



nature of losses or suppressions, e.g. the loss of the last pleurobranch, 

 the loss of the exopodite of the third maxillipede, the loss of a flagellum 

 on the anteimule, the reduction of the antennary scale, and the abortion 

 of the eyes. These are probably degenerative changes without special 

 adaptive significance, and permitted by the absence of competition with 

 other aquatic forms. A study of the gills of Engseus shows that they 

 agree with those of Astacopsis and differ entirely from those of either 

 C/iseraps or FarachserajJs. Thus the Australian Parastacidae show two 

 divergent lines from a common ancestor — the Astacopsis line and the 

 Chseraps line. 



Development of Compound Eye of Crustaceans.* — Th. Moroff 

 gives an exhaustive account of the appearance of the primordium of 

 the eye in Faleemon and Artemia, the development of the optic ganglion, 

 the differentiation of the ommatidia including the formation of pigment, 

 rhabdome, lens, and crystalline cone. He brings out the difference 

 between the crustacean eye and the insect eye, which have phylogene- 

 tically nothing in common. It may be that the insect eye has arisen 

 by a process of aggregation of simple eyes, but a similar kind of aggre- 

 gation cannot be maintained in regard to the crustacean eye. Nor is 

 the frontal eye of a nauplius comparable to an ocellus. Moroff is more 

 inclined to trace back the crustacean eye to the ciliated wreath of a 

 trochophore larva. 



Development of Muscles in Crustacea.f — Th. Moroff finds that 

 in Copepods {Paracalanus and Centropages) an embryonic muscle-tissue 

 arises from the active division of a few myoblasts. The nuclei are 

 much larger and richer in chromatin than those of other cells of the 

 body. 



The myoblasts take their origin from other tissues of the young 

 animal, the nuclei passing into a state of extremely intense vegetative 

 activity, as shown by the accumulation of chromatin. 



After the embryonic muscle-tissue has reached its finaj amount, there 

 occurs in some species of Copepods a dissolution of the nuclei, with the 

 result that an extensive chromidial mass is formed. From this chro- 

 midial mass the muscles of the adult are differentiated. 



In Decapods also {Palaemon) much the same occurs. There is an 

 active accumulation of chromatin and nuclear multiplication. After 

 the greater part of these nuclei are dissolved, the material is formed 

 from which the definitive muscles are differentiated. In all cases a 

 muscle-fibre is not a differentiation-product of one cell, but the material 

 of many cells is used in its formation. 



"Porcupine" Isopods.J — T. P. R. Stebbing describes in the tribe 

 Flabellifera G7iathia cristatipes sp. n. from the English Channel, G. 

 schistifro?is sp. n. from the west of Ireland, and another species from off 

 Yigo, Spain. In near agreement with Gnatliia is the new genus ATcido- 

 gnathia, represented by A. mdipus from Pockall Bank. The oral 



* Zool. Jahrb., xxxiv. (1913) pp. 482-558 (10 pis. and 7 figs.). 

 + Zool. Jahrb., xxxiv. (1912) pp. 559-620 (3 pis. and 9 figs.). 

 X Trans. Zool. Soc, xx. (1913) pp. 231-46 (3 pis.). 



2 K 2 



