206 PROCEEDINGS OF SOCIETIES. 



QUEKETT MiCBOSCOPIGAL ClUB. 



Ordinary Meeting, December 17, 1875.— Dr. Matthews, F.R.M.S., 

 President, in the chair. 



Mr. Ingpen gave a description of the various methods employed 

 from time to time for measuring the angular apertures of objectives. 

 Commencing with that of Mr. Lister, which was the only one in 

 general use prior to 1854, he gave a detailed account of the improve- 

 ments effected by Mr. Wenham, Mr. Gillett, Dr. Robinson, and others; 

 and concluded with some remarks ujion angular aperture generally, 

 with reference to the various opinions held ujjon this somewhat vexed 

 subject. 



Ordinary Meeting, January 28, 1876.— Dr. Matthews, F.R.M.S., 

 President, in the chair. 



Mr. Ingpen described a portable binocular microscope recently 

 constructed by Mr. Swift. This instrument not only packed in an 

 extremely small space, but also comjjrised several contrivances of 

 great convenience. The binocular body, when not in use, could be 

 turned in front, so as to be quite out of the way. The rack was of 

 sufficient range for the lowest powers. The stage was extremely thin, 

 and had a countersunk rotating ring, into which an extra selenite or 

 mica film could be introduced, or it could be used for the examina- 

 tion of diatoms, &c., by oblique light. The compound achromatic 

 condenser was focussed by means of a diagonal slot instead of rack- 

 work ; and the analysing prism moved in a slot above the binocular 

 prism, and was thus always ready for use. These and sundry other 

 arrangements made the instrument very comj)lete and effective as well 

 as extremely portable. 



Mr. T. Curties read a paper by Mr. Henry Davis, F.R.M.S., " On 

 a Larval Cirripede," a specimen of which was found by him on a 

 feather of a sea bird shot about 500 miles N.W. of the Cape of Good 

 Hope. It was at first suj)posed to be the egg of a parasite, but closer 

 examination proved it to be a crustacean, an advanced larval form of 

 Lepas pectinata. The paper contained a minute descrij)tion, and 

 details of the development of this interesting Cirripede, and was 

 illustrated by drawings and specimens. 



Mr. A. Hammond read a paper " On a Comparison of the Meta- 

 morphoses of the Crane-fly and the Blow-fly," in which he endeavoured 

 to show that the former insect forms an exception to the rule enun- 

 ciated by Dr. Weismann, wherein he expresses his belief that "in all 

 those insects in which the anterior larval segments are unju'ovided 

 with api^endages (legs) the head and thorax of the imago are entirely 

 re-developed." Mr. Hammond stated his belief that in this insect the 

 imaginal disks, if such they were entitled to be called, were to be 

 regarded rather as invaginations of the newly forming jjupa skin than 

 as independent centres of growth, commencing in separate closed cap- 

 sules. He described eight pairs of these disks as occurring in the 

 crane-fly, and particularly adverted to the superior pro-thoracic disks 

 as being concerned in the formation of corresponding appendages. 



