76 Miscellaneous, 



Thyridopteryx has its halves united by a double commissure, oue 

 portion crossing above and the other below the oesophagus. When 

 the nervous system has been separated from the superficial ecto- 

 derm, a median ingrowth of ectoderm occurs in Thyridopteryx be- 

 tween the nerve-cords. The cells composing this ingrowth elongate 

 and lie close to the nerve-cords. 



At this stage it appears as if this media)i ingrowth were uniting 

 the cords and forming a commissure, as Hatschek claimed for the 

 Lejndoptera studied by him. This, however, does not prove to be 

 the case. In a subsequent stage the elongated epithelial cells 

 undergo division and give rise to migratory cells corresponding to 

 other migratory mesoderm cells. Cells of this nature invest the 

 nervous system, forming its peritoneal coat, but take no part in the 

 foiTnation of its commissure. The three pairs of thoracic limbs are 

 conspicuous fi'om their size in all embryos studied. 



In the grasshopper both maxilla3 have two lobes outside of and at 

 the base of the main axis of the appendage. These recall, though 

 they are probably not homologous with, the exopodites and epipo- 

 dites. of the Crustacean appendage. Similar lobes have been 

 described by Patten for the maxillse of Blatta. Tracheal invagina- 

 tions occur in the maxillary segments of the grasshopper. In con- 

 clusion, it remains to mention an interesting stage of the spider- 

 embryo in which an abdominal appendage is being converted by a 

 process of invagination into a lung-book. — Johns Ho]_}l:ius University 

 Circtdars, no. 49, May 1886, p. 85. 



Ifotes on the Embryology of the Gasterojiods. 

 By J. PlayfaiPv McMurrich. 



In a number of the ' Studies from the Biological Laboratory,' 

 which will appear during the coming summer, I intend publishing 

 a detailed and illustrated account of the results of my studies during 

 the past winter ujion the development of some marine Prosobranch 

 Gasteropods. In the meantime, however, it is desirable that a brief 

 abstract of some of the more important results should be presented. 



The forms studied principally were Fidgur carica and Fasciolaria 

 tulijxi. The former furnished material for the earlier stages of 

 development, while of the latter I studied only the more advanced 

 embryos. The modes of segmentation of a few other forms, such 

 as Purpura jioridana, Crepldida, and Eupleura caudaia, were also 

 observed. 



The first portion of my paper will deal with the ovum and the 

 nutrition of the embryo, the non-development and employment as 

 nutrition of the majority of the ova in each capsule of Fasciolaria 

 being described and compared with other phenomena of a similar 

 kind. In Purpura Jlor id ana a certain number of the ova, after seg- 

 menting regularly for some time, break down, and aie employed as 

 food by the survivors ; in Crepidida we see the same process, but 

 in a much less marked degree ; while in Neritina it is carried to a 

 greater extent, only one egg, out of a great number which, in each 



