275 



of the egg at stages earlier than this (except of course in the earliest 

 stages when all the nuclei are imbedded in the yolk) ; there is no »re- 

 tarded migration« to the surface of any cells, but all the vitello- 

 phags are derived from cells whose ancestors reached the surface of 

 the egg. 



The cells of the mesoderm plug, soon after their over-growth by 

 the ectoderm, scatter, the majority passing forwards to form the meso- 

 derm of the head and anterior body region, while others, apparently 

 taking on a teloblastic function, are carried back along with the ecto- 

 dermal teloblasts, and give rise to the mesoderm of the posterior por- 

 tions of the body. 



These statements are, in many respects, very divergent from those 

 of previous authors on Isopod embryology. They are given however 

 after a careful study of the problems involved as presented in Jaera, 

 and as definite proofs of their correctness as are possible will be given 

 later. In the meantime it may be stated that, if correct, they serve to 

 bring into closer harmony the modes of formation of the germ layers 

 of those Crustacea of which we possess an adequate account. Up to the 

 present I have not been able to make a thorough study of Asellus and 

 Porcellio , the two forms which I hope to study for comparisons with 

 Jaera, but I have seen enough of their segmentation to feel confident 

 that in the earlier stages it is identical with that of Jaera, but a much 

 greater number of cells is formed before the concentration towards 

 the ventral surface, which results in the formation of the blastodisc, 

 occurs; and furthermore I have not been able to make out as yet any 

 such structural distinctions between the endoderm and mesoderm as 

 occur in Jaera. 



It is worthy of notice that the longitudinal axis of the embryo is 

 at right angles to the first cleavage plane. 



University of Cincinnati, U. S. A., May 9th 1S92. 



II. Mittheilungen aus Museen, Instituten etc. 



Linnean Society of New South Wales. 



May 25th, 1892. — 1) Catalogue of the described Hymenoptera of 

 Australia. Partii. ByW. W. Froggatt. This part, in which 528 species 

 are recorded, completes the catalogue , and is concerned with the following 

 families : Scoliidae, Pompiliidae, Sphegidae, Larridae , Nyssonidae , Philanthi- 

 dae, Craironidae , Bembecidae, Masuriidae, Eumenidae, Vespidae, Andrenidac, 

 and Apidae. — 2) On twenty-one new species of Australian Lepidoptera. 

 By T. P. Lucas, M.R.C. S.E. The species described as new are all from 

 Queensland, and include representatives of the Bombycina , Geometrina, and 

 Nocturna. One new genus, allied to Rivula, is proposed. — 3) Further Notes 



