PROGKESS OP MICROSCOPICAL SCIENCE. 145 



the transformation of heematoblasts, not only into coloured blood-cor- 

 pnscles but also into blood-vessels. The latter takes place in either 

 of the following manners : — (a) Hsematoblastic elements, having be- 

 come vacuolated, lengthen themselves, coalesce at their extremities, 

 and after the disappearance of their corresponding sej)ta a blood-vessel 

 is finished, which in many instances contains new-formed blood-disks. 

 Or (h) a number of haematoblasts — the offspring of bone-cells — which 

 lie in the absori)tion cavities, become fused together so as to form mul- 

 tinucleated masses ; the central part of these gives origin to blood- 

 disks, whereas the peripheral nucleated portion represents the wall of 

 a blood-vessel, a row of such structures having coalesced mth each other. 

 Having formerly stated that in the calcification region cartilage-cells 

 give origin to coloured blood-corj)uscles, Heitzman now finds that 

 blood-vessels are formed at those places as well, the central yellow 

 shining portion — haematoblastic portion — of the cartilage-cells being 

 transformed into a vesicle filled with blood-corpuscles. These vesicles 

 are in general pear-sha2)ed ; one of their extremities, that which is 

 drawn out into a thin solid process, being dii'ected towards the centre 

 of the bone. From the fusion of several such vesicles a blood-vessel 

 proceeds. In a similar way a rajiid formation of blood-vessels from 

 cartilage-cells is to be found in inflamed as well as in new-formed 

 cartilage, e. g. in the callus of fractures. 



The Reproduction of Duckweed in Winter. — Professor Biscoe gives 

 a paper in the 'American Naturalist' (May), illustrated by drawings, 

 of microscopic work undertaken with a view of testing the mode by 

 which the minute white " winter fronds" of Lemna polyrrhiza develop 

 into the well-known green summer flowering and rooting fronds. He 

 finds that the rudiments of both leaf-buds and roots are to be detected, 

 by careful dissection, in the apparently de;id winter fronds. 



Professor Agassiz's New Mode of Teaching.— At the opening of the 

 new School of Natural History, at Penikese Island, the other day. 

 Professor Agassiz, in his opening address, said : — "Our chief work will 

 be to watch the aquariiuu. I want you to study principally marine 

 animals. The only way to do that properly, is to have them alive by 

 your side. In a very few days I shall place at your disposal a series 

 of these appliances. I have ordered one for every person admitted to 

 the school, so that each of you will have means to make these investi- 

 gations. I have never had, in my own laboratory, better opportunities 

 for work than I place at your disj^osal. Our way of studying will be 

 somewhat diflerent from the instruction generally given in schools. I 

 want to make it so very different, that it may appear that there is 

 something left to be done in the system adojited in our public schools. 

 I think that pupils are made too much to turn their attention to books, 

 and the teacher is left a simple machine of study. That should be 

 done away with amongst us. I shall never make you repeat what 

 you have been told, but constantly ask you what you have seen your- 

 selves." 



Development of the Ovide and Fertilization in Primulacece. — Pro- 

 fessor 1'. M, Duncan read a very important paper on this subject at the 



