1888.] MICROSCOPICAL JOURNAL. 77 



may be safely exposed a moment to the heat, to make sure of it, and then 

 covered with balsam and glass as usual. 



The investigator has now before him all the elements necessary for solving 

 his specific problem, according to the formulas which follow : — the normal 

 sponge, the dermal film, the transparent gemmule, and a display of the de- 

 tached spicules. Neither would alone answer, but the series will settle all 

 points, excepting in the case of the genus Carterius. When this is sus- 

 pected the gemmules should first be examined dry ; and, in preparation for 

 mounting, great care should be taken to avoid the destruction of the tendrils 

 (cirri) by the prolonged use of strong acid. Expert microscopists will improve 

 their gemmule mounts by dividing some of them with a thin knife, endeavor- 

 ing to make the section through the foraminal aperture. This, in the case of 

 species having long birotulates, such as JSIeyenia craterifoi-mis^ is of the 

 utmost importance. 



' Seniors' in microscopy will please pardon the minutice of the processes 

 just given as they were necessary to make them available for the 'freshmen.' 

 All are reminded that the above directions as to collection and examination 

 refer to mature sponges only. It is seldom safe, or even possible, to ?7.ame 

 one in which no gemmules can be found. If a course of study is under- 

 taken involving the histology and physiology of fresh-water sponges, many 

 peculiarities will of course be obsei-ved that have not been alluded to here. 

 One of them concerns the development of the spicules, and if not under- 

 stood will pretty certainly mislead the beginner into the supposition that he 

 is examining a novel species. Both the skeleton and dermal spicules of 

 young sponges are frequently marked with bulbous enlargements at the 

 middle, and often half way between the middle and each end of the spicule. 

 These seem to indicate an immature condition, as they disappear when the 

 spicules are fully formed. 



EDITORIAL. 



We announced some time since (Journal, viii, p. 134) that Mr. A. J. 

 Doherty , of Manchester, would shortly visit this country. The plan then pro- 

 jected was interfered with, but Mr. Doherty has lately written again concerning 

 his intentions. From his letter we quote the following : — • I am in negotiation 

 with the San Francisco, the Denver, and the Welleslev College Microscopical 

 vSocieties as to my giving before them demonstrations in practical microscopy. 

 It is quite possible that I shall leave here for the United States towards the 

 end of March, or early in April. * * * I feel certain that the demonstra- 

 tions will be both interesting and instructive, and the exhibit of slides, etc., 

 with the lantern microscope, will give pleasure to all who witness it.' 



The demonstrations include animal and plant section cutting, single and 

 double staining, anatomical injection, selecting and arranging foraminif- 

 era, mounting in balsam and other media, construction and use of the lantern 

 microscope. Any societies which are prepared to secure one or more of the 

 demonstrations will unquestionabh- derive very great benefit, and we shall be 

 glad to correspond with them relative to the matter. 



CORRESPONDENCE. 



Making Mounts Photographic. 

 To The Editor : — There is a phase of mounting which could well be impressed 

 upon the attention of microscopists. That is, to make all mounts with reference not 

 merely to use under the tube, but with reference to good photographic results. I 



