94 CO. R. Osten Sacken: on Mr. Portchinski's publications 
on the contrary they oceur in various families, among species living 
upon entirely different substances. Mr. Portchinski argues therefore 
that if the biological conditions of the coprophagous diptera are so 
peculiar as he represents them, it follows that in whatever family 
or group they occur, their biology would necessarily be different from 
that of the other species in the same group. He goes on to show 
that coprophagous diptera, in whatever family they occur, incline to 
viviparousness. Ameng the viviparous diptera par excellence, 
the Sarcophagae, there is a coprophagous species, 8. haematodes; 
the coprophagous Mesembrina meridiana is viviparousı), while the 
other species M, resplendens lays eggs; the coprophagous Dasyphora 
pratorum is viviparous, while D. lasiophthalma lays a quantity of 
eggs. The Hylemyiae lay eggs, but among them there is a copro- 
phagous species, A]. strigosa which is viviparous- Even in other 
families systematically distant from the Museidae, the biology of co- 
prophagus species is peculiar. The most striking example is Chiro- 
nomus stercorarius, which ‚forms a remarkable exception among 
all the Nemocera in being viviparous. 
There are different modes of viviparousness, most interesting 
to study. The coprophagous species of Sarcophaga do not lay more 
than 40—60 larvae, but of large proportions; these larvae in deve- 
loping in fecal matters go through all the three stages of development. 
Hylemyia strigosa, which is only 5 mm. long, deposits in fecal 
matters a single larva (very seldom two), which develops within the 
body of the fly from an egg of a proportionate size. One ‚might 
expect, from the comparatively enormous size of the larva, that it 
is brought forth in the last stage of its development. But this is 
not the case. This at its birth gigantie larva, is still in the first 
stage, and has the characteristic heart-shaped opening of the stig- 
mata; it soon passes into the second stage, with two fissures to the 
stigmata, and then into the third, with three fissures (figure 7). 
These various modes of development of coprophagous diptera 
(viviparousness, or oviparousness, with omission of the second stage 
of the larva, or laying of a single very large larva), — all have the 
same end in view, — the gain of time, the shortening of the period 
of growth. And it is remarkable that, within one and the same 
genus, different species take different roads towards that end; for 
1) The observation on the viviparousness of Mesembrina meri- 
diana was made in the Crimea. A larva 3 mm. long was found in 
the body of a female, and alongside of it an egg of the same length. 
The further development of the larva has not been investigated. 
