88 PROGRESS OF MICROSCOPICAL SCIENCE. 



the right-hand individiial, which, with the remaining projection of the 

 isthmus, appeared broadly coniform in outline. In the left-hand indi- 

 vidual all remains of the isthmus at once disappeared, and the animal 

 appeared reniform in outline, but now contracting on the same side it 

 assumed the biscuit form. The constriction rapidly increased, and in 

 thirty minutes from the time of separation from the right-hand indi- 

 vidual it divided into two separate animals presenting the ordinary 

 appearance of A. Sol. Thus this second division took place in an 

 opposite direction from the first. The right-hand individual, retaining 

 the oil globules apparently unchanged, more slowly assumed the reni- 

 form outline, and then became constricted all around. The constriction 

 elongated to an isthmus, in the centre of which were the oil globules. 

 Three hours after the separation of the right-hand animal, the isthmus 

 was narrowed to about half the diameter of the two new individuals 

 which were about to be formed. At this moment other engagements 

 obliged me to leave the examination of the animals. Six hours after, 

 in the animalcule cage, I observed only half-a-dozen individuals of 

 the A. Sol. 



TJie Fresh-icaier Algce of North America. — Students of our fresh- 

 water algfe will find in the beautiful and interesting work of Dr. H. C. 

 Wood, jun., says the ' American Natiu'alist,' ' A Contribution to the 

 History of the Fresh-water Algte of North America,' a ready means of 

 identifying their siiccimens. It is a large quarto volume, with many 

 coloured plates, and is taken from the Smithsonian Contributions to 

 Knowledge. 



Development of Ferns without Fertilization. — At a late meeting of 

 the American Academy of Arts and Sciences, Prof. Gray communicated 

 a paper by his former pupil. Dr. W. G. Farlow, now in Germany, on 

 the development of ferns from the prothallium irrespective of fertili- 

 zation, by a sort of parthenogenesis. The growth obseiwed took 

 place, not from an archegonium, but from some other part of the 

 prothallium. 



Miijration of White Blood Corpuscles. — Dr. Thomas read, before 

 the German Association of Naturalists at Wiesbaden, a paper on the 

 migration of the white coi'puscles into the lymphatics of the tongue of 

 a frog, which is thus abstracted by the 'Lancet': — He injected the 

 lymphatics of the living animal with an extremely dilute solution, not 

 containing more than 2-fyL-jjth to ^-^jj-^ih. part of nitrate of silver, and 

 found that, with certain precautions, this did not lead to stasis of the 

 blood in blood-vessels, but only to a lively exodus of the white cor- 

 puscles from their interior. After the lapse of some time, when the 

 parts had begun to recover from the injurious effect of the injection, 

 he was enabled to observe the re-entrance of the corjmscles into the 

 lymphatic vessels, through certain stomata in their walls, now marked 

 and rendered distinct by a precipitate of the silver salt. In a second 

 series of researches the lymphatics were injected with a dilute emulsion 

 of cinnabar, in a f per cent, solution of common salt. The cinnabar 

 was in part deposited in the stomata of the lymphatics, and partly 

 passed through them, and was deposited in the tissues in the form of 



