351 



beset Avith numerous seta, each implanted at the anterior margin of a 

 granule: and between these granules a large number of tiny grooves 

 are seen. The posterior margin of the cervical groove is armed with 

 a dense row of setae (see Fig. 1). It seems probable that these features 

 stand in connection with some biological peculiarities of these cray- 

 fishes. The structure of the carapace on the branchial chamber seems 

 to be apt to retain the humidity longer on this place than if it was 

 smooth and this might be of use if the crayfishes should make any 

 excursions on dry land. The inner surface of the carapace covering 

 the branchial chamber is also very densely hairy which also serves the 

 same purpose to retain the water. The armature of the cervical groove 

 would help to carry water (rain?) from the back to the anterior bran- 

 chial opening along the cervical groove. 



I am indebted to Mr. P. Du s é n for the following interesting infor- 

 mation concerning Parastacus Hassleri. The places, where these cray- 

 fishes lived, were slightly sloping, moist meadows. The humidity on the 

 surface was however not greater than that Mr. D us en could walk there 

 with dry shoes. It was no open water whatever, lake or river, in the neigh- 

 bourhood. Here they crayfishes had made vertical holes in the earth and 

 round these holes they had erected »mudchimneys« out of the clayey 

 material which they had carried up from their burrows. These chimneys 

 had often a height of 2 — 3 deem ; but were sometimes lower and some- 

 times there was only a heap of earth like a small molehill round the 

 opening. In the latter case Mr, Dus en expressed as his opinion that 

 possibly the rain had broken down the »chimney« because there were 

 often heavy rains while he visited these parts. The crayfish is edible 

 and offered for sale in the market. It is caught by the native boys 

 which thrust their arms in the above mentioned holes and by making 

 pumping motions they soon draAv up water and with that the crayfish. 

 It is apparent from this description that these crayfishes lead a sub- 

 terranean life in the groundwater. But I hardly think that they can 

 find sufficient food in their barrows. It seems therefore probable that 

 they leave their homes during night time and in the rainy season and 

 make excursions on the surface. Such habits would explain the above 

 described structure of the carapace. There are however many biologi- 

 cal features of these and related animals which need to become better 

 known and explained. Parastacus is not alone in its subterranean 

 habits. Faxon in his mentioned papers gives references from different 

 authors which have observed similar habits in species of Cheraps, 

 Camharus a. o. ; some Camhari even building »mudchimneys«. In 

 Florida I sometimes saw Cainhari in holes which were quite remote 

 from the nearest lakeshore but the holes had usually reached the 



