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PROGRESS OF MICROSCOPICAL SCIENCE. 
of two centimeters by the end of May, and were without a trace of the 
hind legs. By the 1 Oth of June the former had their fore legs, and 
some were changed to frogs; the latter, still black, had no trace of 
legs, and breathed almost exclusively by means of their gills. By 
the 15 th of July all the former had become frogs ; but those of the 
latter still had no legs, and by the 2nd of August they were a'll dead, 
without a trace of legs having appeared. Some of the young of the 
latter lot transferred to the vessel of the former on the 15th of July 
finished their metamorphosis. At the same time, some of the former 
transferred to the vessel containing the latter continued to develop, 
showing the influence of the first impulse in their development. 
The Eozoon Question — An American Mistake. — In a notice of a book 
on the geology of New Hampshire, in ‘ Silliman’s American Journal,’ 
March, 1875, the writer makes the following remarks: “On the 
question of the animal nature of the Eozoon, Professor Hitchcock 
writes judiciously, excepting in a single remark. He observes that 
‘ those who disbelieve the organic theory are mostly better skilled in 
mineralogy than biology.’ But Messrs. King and Rowney, the chief 
contestants, are not mineralogists, but zoologists, and Mr. Carter, of 
England, another strong opponent of the £ organic theory,’ is also a 
zoologist, and one particularly versed in the lower orders of animal 
life. There are probably mineralogists that doubt, as there certainly 
are zoologists, but we can recall no articles by any such on the sub- 
ject, excepting one or two which aim to show that the limestones 
containing Eozoon are sometimes of igneous origin, an observation 
which, whether sustained or not, cannot be attributed to mineralogical 
prejudices.” To this we may observe, that Professor King is essentially 
a geologist, and not a student of microscopic structure ; whilst Pro- 
fessor Rowney is exclusively a chemist. 
The Poppy Fungus. — The ‘ Academy,’ in a late number, points out 
that Dr. Cunningham (whose memoir we have not received) states 
that this fungus, which is so destructive to the opium crop, is a near 
relative of the potato blight, and is named Peronospora arborescens. 
Dr. Cunningham found that soaking fine sections of the poppy leaves 
in carmine solution enabled the mycelium threads, which took up the 
colour, to be traced running between the cells, but not in any case 
perforating them. The conidia , which crop out abundantly from the 
fertile filaments on the under surface of the leaves, he states, “appear 
very rapidly to lose their power of germinating.” He was unsuccessful 
in his search for the oogonia and oospores, supposed from analogy to 
exist in these fungi and spring from the mycelium in the tissues of the 
plant. Oospores can preserve their germinating power for months, 
and are conjectured to be important means of propagating the Perono- 
spora moulds. As the Peronospora arborescens, or poppy mould, is 
common on wild poppies in this country, English microscopists may 
contribute to the further elucidation of its life history. 
The Dimorphic Development of the Cladocera. — A late number 
(March) of ‘Silliman’s American Journal’ points out that Dr. G. 
Sars has discovered a remarkable dimorphism and alternation of 
