of Cecidomyide Larve. 165 
acquired a somewhat tougher consistence, and is still covered by 
the common tunica propria. 
I need hardly state expressly that the organs here described 
are nothing but the germ-stocks of our larve. The certain con- 
viction of the correctness of this assertion is indeed attained only 
by their subsequent behaviour when we see that the individual 
balls gradually become more sharply and independently separated 
from each other, and finally (fig. 4) break loose in order to pass 
through their embryonal development in the body-cavity. 
In general, however, the mass of the germ-stocks does not 
break up at once into its constituent balls, but gradually; so that 
its remains are sometimes found in individuals in whieh the free 
germs have already grown to a considerable size and show indi- 
cations of the embryonic structure. In this way the fact noticed 
by previous observers, that the germs of our larve are by no 
means always met with at the same stage of development, may 
also be explained. 
The balls when ready for separation are about 0:028-0-03 
millim. in diameter. They have (Pl. I. fig. 4) a perfectly glo- 
bular form, and exhibit, beneath the structureless clear and 
transparent enveloping membrane, two different kinds of cells. 
Some of these are small (0-0063 millim.) and sharply defined, 
and are united to form an epithelium which clothes the mner sur- 
face of the above-mentioned membrane ; whilst the others, which 
fill the interior space of the ball, are of much larger size, and so 
imperfectly discriminated from each other that they almost pre- 
sent the appearance of a coherent mass of protoplasm in which 
numerous vesicular nuclei (0°007 millim.) are imbedded. The 
contexture of these central cells reminds us of the behaviour of 
the primitive germ-stock, only that here the protoplasm is less 
massive and is destitute of the small, strongly refractive oil- 
globules which are deposited in larger or smaller quantities round 
the individual nuclei. 
The genetic relations of these mature germ-balls to the previous 
stages of development are easily understood. The cells which 
we met with in the latter, although then without any differences, 
have become, by gradual differentiation, partly converted into 
epithelial cells and partly into structures which, by their histo- 
logical nature, sufficiently show that they have still to pass through 
a further development. 
After separation, however, the germ-balls for a time retain the 
structure just described*. They grow to a diameter of 0:04 or 
* For comparison we may here cite Pagenstecher’s description of the 
youngest germs observed by him. ‘‘'Phey consist,” says our author, “of 
a peripheral layer of small clear globules, in which neither membranes nor 
nuclei are distinct, and of an interior space enclosed by these, in the hemo- 
