41 
practical reasons”) quantitative investigations have not yet been carried out here, 
but it may be said with certainty that this is the region of the small gastro- 
pods, Rissoa, Trochus, Cerithium, Littorina, Lacuna and Nudibranchs; here we 
also find Modiolaria (marmorata, discors) and Mytilus, mostly young, as also a 
quantity of Amphipods, Isopods, and all the animals which swarm on the Zostera, 
as Hydroids, Actiniae, Echinus miliaris, Ascidians (Ciona, Clavellina), worms etc. 
Inside the Zostera, on more or less pure sand bottom, often with stones, we meet 
lastly the strand-fauna with Fucus and other algae as the characteristic plants. In 
the pure sand in here live Mya arenaria, Cardium edule, Tellina tenwis, Arenicola 
marina and on stones and plants especially Acmaea, Chiton, Littorina littorea, Balani 
etc.; in this innermost belt quantitative investigations are also difficult, among 
other reasons because the »Sallingsund« cannot go in on such shallow depths and 
the apparatus is too heavy to be used from an ordinary boat. In the Sound this 
belt is further out in deeper water, 3—9 feet, and some quantitative determina- 
tions were carried out here, Table VI, Snekkersten. The fauna of the pure sand 
bottom resembles the fauna on the clay bottom with regard to the life; it consists 
of Molluses and worms, which are detritus-feeders; but the remaining, plant- 
covered part of the strand-belt and the fauna of the Zostera belt is, as has been 
shown in the above sketch, more mixed. Here live Lamellibranchs (Modiolarta) 
and Ascidians as detritus-feeders, which obtain their detritus from the water 
itself, along with Gastropods which either feed upon the Zostera itself or its 
algal vegetation, or they lick off the slime on the surfaces of the older leaves 
of the Zostera, on the stones or other objects, oysters and the like. Acmæa and 
Chiton actually keep the upturned shells of oysters free of plants, but in doing 
so dig deep passages in the shells. Littorina littorea is used at certain places to 
keep the oyster basins free of the algae which grows on them. 
From my experiments with bundles of twigs, stones, shells and such like 
objects, laid out for the oyster spat to attach themselves to, I know how quickly 
such objects in the Limfjord become covered with a slimy layer consisting of 
quite small plants, among which certainly bacteria and lower algae play the most 
important part; to get the spat-catchers out just at the right moment is the main 
thing, as the layer of slime prevents the small oysters from attaching themselves. 
The Gobies also seek for clean objects to fasten their eggs on and in the spaw- 
ning-time almost every object which is laid out on the bottom, such as anchors, 
stones, cigar boxes and the like, are covered over with the eggs in the course of 
24 hours. This shows, how much clean objects are sought after, in other words, 
how much the algal slime occurs in these plant belts, where the influence of 
the light is still felt strongly right to the bottom. The blades of Zostera, with 
exception of the very young, are all covered over with this slime, and every one 
knows the large colonies of algae and diatoms which grow on the Zostera and 

t) In the Tables I—III (cf. Chart I) some of the stations 91—100 at any rate should 
perhaps rather be referred to the Zostera belt, on almost all of them some Zostera grows as a 
matter of fact. The animals taken there are also essentially different from those of the other 
stations; there does not seem to be very many of them. Regarding the animal life of the 
Zostera region in general, I cannot venture to express an opinion, so far as the quantity is con- 
cerned, until further investigations have been carried out. 
6 
