CHAP. XVI 



HABITS 



451 



Fig. 226. A piece of a matted colony of 

 Ph. kowalevskii Cald. Slightly magnified. 

 In most cases the tentacular head is 

 protruding from the tube. 



What little we know about the habits of PhororvU is in the 

 main due to the observations 

 of Cori, 1 who studied Ph. psam- 

 mophila at Faro, an inlet of 

 the sea near Messina. The least 

 disturbance causes the animal 

 to withdraw its head with 

 lightning rapidity into the 

 tube, from which after a time 

 it re-emerges very slowly, and 

 does not expand its tentacular 

 crown until its body is completely extended. Cori states that 

 not unfrequently individuals are found either without the crown 

 of tentacles or with the latter in process of regeneration. These 

 may have been bitten off by fish, etc. ; but, on the other hand, 

 van Beneden describes in Cre/pina gracilis {Ph. hippocrepia) the 

 throwing off and regeneration of the crown of tentacles ; and 

 Cori confirms his observation, at any rate as far as concerns 

 those individuals kept in captivity, and whose surroundings were 

 presumably somewhat unfavourable. He further observed the 

 interesting fact that the cast-off' crown of tentacles continued to 

 live, and suggests that possibly it may develop a new body, in 

 which case the phenomenon would be an interesting case of 

 binary fission producing two new animals. 



With regard to the habitation of Ph. australis, the largest 

 species known, some discrepancies have crept into the literature 

 of the genus, and to prevent their recurring again it may be 

 worth while to quote the statements of its discoverer, Mr. 

 Haswell. 2 He says : " Phoronis australis occurs in commun- 

 ities of twenty to thirty, in spaces in the substance of the 

 wall of the tube inhabited and formed by a species of Ceri- 

 anthus. Each worm has a tube of its own, very delicate and 

 transparent, made up of several layers, the mouth opening on 

 the outer surface of the tube of the Cerianthus. The Cerianthus 

 tubes sometimes come up empty, as we should naturally expect, 

 the animal having dropped out ; but a sufficient number of 



1 "Beitrage zur Anatomie der Phoronis," Inaug. Dissert. Prog. 1889, and 

 Zeitschr. iviss. Zool. vol. li. 1891, p. 480. 



2 P. Linn. Soc. X. S. Wales, 1st ser. vol. vii. 1883, p. 606 ; and 2nd ser. vol. 

 vii. 1893, p. 340. 



