PROGRESS OF MICROSCOPICAL SCIENCE. 101 



together more closely iu the transverse direction than in the longitu- 

 dinal would account for the elongated form of the pseudo-hexagons 

 when seen. Some parts of the photographs closely approach Hart- 

 uack's description, but it is easy to observe that these are not the parts 

 which are most nearly in focus. He has also resolved this diatom by 

 monochromatic light derived from the electric lamp. The appear- 

 ances obtained were identical with those above described. 



Mr. Lowne on Pangenesis. — At a late meeting of the Quekett Club, 

 Mr. Lowne, in making some observations on the white blood corpuscles 

 of the newt, made some forcible remarks on the subject of Pangenesis. 

 He recorded the experiment of Cohnheim on the blood corpuscle. 

 If the swim bladder of a fish be filled with a solution of common salt, 

 containing one per cent, of salt, tied and inserted under the skin of 

 a rabbit or frog, after a short time, say twelve or twenty-four hours, 

 it would be found filled by a large number of leucocytes, which had 

 found their way into the bladder by permeating its walls. These were 

 alive when they left the living tissue of the animal, but after going 

 through the bladder their movements no longer continued, as they died 

 in the saline solution ; hence they were unable to escape from the 

 bladder, and a large number became entrapped. This result not only 

 applies to the swim bladder of the fish, for, according to Cohnheim, if 

 the cornea of a frog's eye be taken (it must be quite fresh) and inserted 

 under the skin of a living frog, in the course of twenty-four or forty- 

 eight hours it will be found upon examination to contain a large 

 number of leucocytes at various depths in the tissue of the cornea. 

 Mr. Lowne considered these to be very remarkable properties, and he 

 laid much stress ujwn them as throwing a great deal of light upon the 

 doctrine of Pangenesis, as enunciated by Charles Darwin, by which 

 doctrine it was supposed that particles or gemmules were given off 

 from every part of the organism, capable of reproducing like parts 

 under certain conditions, and of being collected in the ovum. The 

 whole animal was thus permeated by particles jiassing off from the living 

 tissue. It had been objected to by Dr. Lionel Beale that these parti- 

 cles, being solid, could not pass through the walls of a living cell ; but 

 if leucocytes could pass through solid tissues he could not see why 

 minute gemmules, which might be solid or semi-solid, like leucocytes, 

 should not pass through cell walls. He could nut see why there should 

 be any serious objection to the doctrine of Pangenesis. There was 

 great difficulty in distinguishing a solid from a fluid. If the Protozoa 

 be examined, many of them would be found to exhibit a series of gra- 

 dations of solid matter, harder externally and softer internally ; but 

 no lines of demarcation could be drawn between the solid and more 

 fluid parts of those animals, as one portion of the protoplasm shaded 

 insensibly off into another. 



The Darwinian Theory applied to Plants. — Certainly the best paper 

 which has yet been published by the ' American Naturalist ' is that in 

 the July number on the above subject. It is of considerable length, 

 abundantly supplied with notes, and is under the joint authorshijj of 

 Dr. E. Mullcr and Professor F. Delpino. It has been translated into 

 English by Mr. R. L. Packard, a gentleman who is himself familiar 



