THE MARINE SAND-DWELLING CILIATES OF CAPE COD

¹ Collége de France, Paris, and Marine Biological Laboratory, Woods Hole, Mass.

1. Two categories of ciliate species dwell in the damp sand of marine beaches; some of these seem to be so closely adapted to interstitial conditions that they do not live outside; some others enter the sand readily and can live in it as well as anywhere else along the seashore, where they are ordinarily widespread.

2. With regard to the size of the interstitial sand spaces, which are roughly proportional to the size of the grains, the sand-dwelling ciliates can be divided into two ecological classes:

In coarse sands, with a mean diameter of the grains above 0.4 mm., the mesoporal infusorian fauna includes a few species exclusively sand-living and many occasional sand-dwelling forms.

In fine sands, with a mean grain diameter of 0.3 to 0.7 mm., the microporal infusorian fauna is composed of true sand-living ciliate species.

In addition, some typical interstitial species, widespread in fine and coarse sands, are called euryporal.

3. Comparison of the ciliate interstitial fauna observed in Brittany and Cape Cod beaches shows that interstitial species are cosmopolitan, and that the distinguishing characteristics of mesoporal and microporal fauna have a generalized ecological significance. On the other hand, it appears that the truly microporal species are endowed with some peculiarities very interesting from the standpoint of cytology, cell-physiology and micro-ecology.