258 
PROGRESS OF MICROSCOPICAL SCIENCE. 
two main tracheae, communicating by two cross branches and sending 
off numerous twigs. The young of the house-fly differs chiefly from 
that of the flesh-fly in being only one half as large, while the form of 
the openings in the spiracles at the end of the body is entirely dif- 
ferent. When about to transform into the pupa or chrysalis state the 
body contracts into a barrel-shaped form, turns brown and liard, 
forming a case (puparium), within which the body of the larva 
transforms into that of the pupa. Weismann has made the discovery 
that in the larval flesh-fly, when about to transform into the pupa 
state, the head and thoracic segments die, and that the head and 
thorax of the pupa arise from minute disks attached to the smaller 
nerves or tracheae in the body of the worm. This is paralleled by the 
metamorphosis of the ' pluteus ' into the adult starfish, and is a much 
more comj^lete metamorphosis than even that of the caterpillar into 
the chrysalis of the butterfly. Our house-fly having as a maggot lived 
a life of squalor, immersed in its revolting food, with its new change 
of form, involving the death of one half its body and the origin of a 
new head and thorax, with legs and wings, eyes, feelers, and mouth- 
parts, after a short pupal sleep of from five to seven days pushes off 
one end of its pupa case, and appears winged, with legs where before 
there were no traces of feet, and is animated by new instincts and 
mental "traits. It is difficult to realize how striking are the changes, 
physical and psychological, which the house-fly undergoes in the 
transition from the maggot to the volant, cursorial being." 
The Fructification of the Basidiomy cells. — A recent number of the 
' Academy ' contains a note on the above subject which refers to 
a paper by Professor Reess in the ' Sitzungsberichte ' of the Phy si co- 
Medical Society of Erlangen. It says of this botanist, that he 
describes the ripe spore of Coprinus stercorarius as opaque and seem- 
ingly homogeneous in a dry state. When it has absorbed water, " the 
inner contour of the brown episporium is plainly seen. The existence 
of the endospore is, however, first proved by the germination. The 
spore-contents exhibit nothing remarkable. The germination of the 
spore occurs in water or on moderately dry dung, upon which it 
ripens. In fresh dung, or dung decoction, it begins in a few hours 
and proceeds quickly ; more so if the decoction is concentrated than 
' if it is weak.' It commences with the extension of a round papilla 
of the colourless endospore from one, or less often from both ends." 
The author describes the formation of rods in diverging groups, of 
which he gives a figure. These rod-cells are spermatia. The 
Coprinus likewise forms corpogouia, figured as rounded swellings 
filled with granular protoplasms. Two other figures show the rod- 
cells attached to the carpogonium cells, which they fructify. The 
sexual organs and fructification of Coprinus, Professor Eeess says, 
resemble those of lichens and floridiae. 
A Curiows Fact in the Development of Bursulla crystallina. — Under 
the name of B. crystallina Professor Sorokine* describes a new genus 
of Myxomycetes in the ' Annales des Sciences Naturelles.' | This 
* 'Academy,' Sept. 30. f Ser. 6, vol. ill. part 1. 
