Videnskabelige meddelelser

Videnskabelige meddelelser


use of the glands in the piates he does not know but he supposes

that they. in some way, play a role during the copulation. This

is of course very probable, especially because they are developed

in both sexes; still it may be supposed with the above cited ob-

servations in mind that these pores, especially in the genus Hij-

cirachna, are used as organs by means of which the mites during

the egglaying processes are glued to the substratum.

These observations interested me very much, especially because

I regarded them as quite new; the paper of Duges being at that

time unknown to me, and often having found the eggs of other

Hydrachnids in nature or in my aquaria, I did not know that the

genus Hijdrachna, with regard to the egglaying, acts in quite

another way than other Hydrachnidæ. I regret very much that I

did not then possess the excellent binocular aquarium microscope;

it was rather difficult with a common lens to see whether the

rostrum pushed the eggs into the orifice or whether they were

pushed down by means of the long outdrawn vulva ; as I often

saw the rostrum in the hole I suppose that this was used.

As is well known the genus Hijdrachnd differs from all other

Hydrachnidæ in the consiruction of the mandibles. They are formed

as a piercing organ and can be pushed out for considerable dis-

tance beyond the lower lip. Pollock has shown that the apex is

sawtoothed. Hitherto we have supposed that this structure of the

mandibles was in accordance with the manner of nourishment and

that the mites by means of them pierced their prey and sucked

it out. From Duges' and my own observations I am inclined to

think that the transformation of the mandibles is in accordance with

the process of egglaying and used as piercing organs by means of

which mines for the eggs are made in soft plant tissue.

The 17/VI the Alisiua piants were brought into the aquaria

and in the following eight days the egglaying took place. The

piants were standing in shadow by a tp. of 15—20 " C. The larvæ

arrived at 7/VlI. The mines were emptied and during the time

from 7 VII to l/VIII the water was reddish owing to the enorm-

ous amount of larvæ. The larvæ swam round with great speed

and were accumulated especially towards the source of light. The

large capitulum is carried bent below the body ; the larvæ never

came to the surface as those of Liinnochares and Eijlæi's. During

More magazines by this user
Similar magazines