10 Mindeskrift for J. Steenstrup. XXVII. 



from the bottom of this issues a canal, which becomes narrower towards the inner 

 opening, and which during the course inwards is about rectangularly bent. The 

 canal is comparatively long, not going the shortest way through the chorion, but 

 running somewhat tangentially in the same. That form of the micropyle quite agrees 

 with the one in Gerris lacustris, described and figured by Leuckart (Muller: Arch. f. 

 Anat. Physiol. und Wissenschaftl. Med. 1855, 158, Taf VIII, fig. 26) as well as the 

 Halobates-egg upon the whole shows great accordance with the Gerris-egg. 



In colour the eggs vary from yellowish white to red or reddish brown ; it is, 

 however, not the eggs of the different species that have a different colour, but the 

 eggs of the single species run through the scale. The faet is that the colour is 

 chiefly dependent on the contents, as the chorion is transparent, and only slightly 

 yellowish; the eggs in which the development has not begun are yellowish white, 

 and gradually as the embryo is developed, the egg grows darker and becomes at 

 last red or reddish brown. The eggs mentioned by Witlaczil (1. c.) are also called 

 brick coloured, and they had fully developed embryos. In the eggs with a very 

 thick chorion this can be a little more yellow than in the thin shelled ones. 



From the above list of the material it is evident that the Halobates-species de- 

 posit their eggs on floating objects of the most different sorts. It is, however, worth 

 remarking that they almost always are of animal or vegetable origin, of course, be- 

 cause such objects most frequently are present. The material contains only two ex- 

 ceptions herefrom, No. 5 and 9, in the former case the eggs are laid on a cork 

 stopper, and in the latter on a small coal-slag. The number of the eggs varies from 

 about 30 to many thousands. It seems as if the females also can lay their eggs 

 without their being fixed to any object. The specimen No. 6 is a longish, nearly 

 band-shaped mass of eggs glued together; only some quite thin threads are to be 

 seen in it, which probably form the original substratum for the eggs, but that ob- 

 ject is so extremely small, that it cannot have been of any importance for the 

 floating power of the eggs ; it must only have been the floating power of the eggs 

 themselves that in this case has supported them. As it seems to be rare for the 

 eggs to be laid in that manner, it probably only happens when the females have found 

 no floating objects. As mentioned before females in some cases have been found 

 bearing 1 — 3 eggs at the end of the abdomen; it may be supposed, I think, that the 

 females bear them only for a short time, till they find a suitable place for depo- 

 sition ; if such a one is not found, they may thus possibly also lay them without it. 



The deposited eggs are attached with a glue-like substance which in my spec- 

 imens is more or less abundant, but it is always distinctly present, and the eggs 

 are solidly fastened. Most frequently the glue-like mass is abundant and surrounds 

 the eggs entirely, and when an egg is isolated, it is seen to be more or less com- 



