ZOOLOGY AND BOTANY^ MICROSCOPY, ETC. 543 



elevations. Insects play a certain part in this circulation of organic 

 germs. The essential composition of the air itself appears to be the 

 same at all heights. 



New Myxomycete.* — V. Fayod describes a new myxomycete, 

 growing on horse- or cow-dung, which may be a form of Amoeba 

 Limax Duj., aud to which he gives the name Guttulina protea. 



It forms yellowish-white, shining, fusiform or horn-shaped eleva- 

 tions from 1 to 3 mm. high, which, when immersed in water, break 

 up into a great number of spores, which are hyaline, colourless, or 

 slightly yellow, strongly refractive, more or less regularly elliptical, 

 bean-shaped, or nearly triangular, with an average length of about 

 14 /x and breadth of about 9 jj.. Their protoplasm is finely granular, 

 and contains a comparatively large, usually central, nucleus. They do 

 not germinate in water, but in a decoction of dung after about 

 20 hours. Shortly before germination a slowly pulsating vacuole 

 makes its appearance, which disappears a few minutes before the 

 protoplasm escapes as a myxamoeba or swarmspore through a lateral 

 orifice in the membrane of the spore, only one being formed in each, 

 spore. 



The free myxamoeba, after moving about for a time, takes the 

 form of a slug and contains a nucleus, the anterior end being occupied 

 by the denser hyaloplasm, the posterior end by the less dense granular 

 protoplasm, where there is also a large slowly pulsating vacuole. 

 Like other amoebae, it has the power of taking up and digesting solid 

 substances. No enveloping membrane can be clearly distinguished, 

 tbough it probably possesses one. Their average length is from 16 

 to 22 j(i ; they move about with considerable rapidity. These myxa- 

 moebae possess a peculiar property of a sudden rapid propulsion, to 

 from two to four times. their own length, accompanied by a temporary 

 rounding off of their shape. 



Multiplication begins some time after germination, when the 

 myxamoeba has attained a considerable size. Its motion becomes 

 gradually slower and at length, ceases ; it becomes round with short 

 blunt projections, which are soon drawn in again, the nucleus at length, 

 disappearing. It now becomes more and more elongated, then hour- 

 glass-shaped as the protoplasm collects at the two ends, and finally 

 divides into two. Each of the two new myxamcebee rapidly assumes 

 the slug-like form of the parent, and developes a nucleus. This 

 process of division is repeated through several generations. It is 

 well observed only in a dilute and pure nutrient fluid. They creep 

 readily out of the nutrient fluid, and then assume indefinite, usually 

 flattened disk-shaped forms. Although apt to collect together 

 in great quantities, coalescence into a true plasmodium was never 

 observed. Under favourable conditions they become transformed into 

 spores, distinguisbed by their rounder form, greater refrangibility, 

 and want of motility. It is only some time after this change that a 

 membrane is distinctly visible. The spores germinate usually in four 

 or five days. 



* Bot. Zlg., xii. (1883) pp. 169-77 (1 pi-)- 



