41 



husMi has a length of about 520 mm., possesses numerous 

 tentacles and some 84 longitudinal muscles. P. australis reaches 

 a size of 127 mm., and also has numerous tentacles and the longi- 

 tudinal muscles number about 47. 



3.-SPECIES OF ACTINOTROCHA. 



De Selys Longchamps showed a disposition to analyse the 

 species of Phoronis with suggestions as to forms which should be 

 united, but in the case of the larvae he contented himself by giving 

 all the varieties which had been described and added a number 

 of his own to the list. Many of the so-called species have been 

 described from mounted and preserved sx^ecimens, and the 

 characters in many cases at least appear to be due to contraction 

 and distortion. The number of tentacles is not sufficient to 

 indicate the species even at the time of metamorphosis. The 

 size is a guide, and indeed the size and the relative number of 

 tentacles are with the general shape all we have to depend upon 

 for distinguishing the species. 



Actinotrocha hranchiata, Miiller. — The characters and dis- 

 tribution of this species have already been considered. It is found, 

 as has been noted, from the Mediterranean to Norway. A. gegen- 

 bauri (Messina), which measures 2-5 mm. and has twelve pairs of 

 tentacles may be included here, and also A. ornaia (Nice) which 

 only differs with respect to pigment, and this is very variable. 

 A. dubia, found at Naples, measured in the contracted condition 

 1 mm., and possessed ten pairs of tentacles ; A. olgae also obtained 

 at Naples, agrees with A. brancMata in size, and has ten pairs 

 of tentacles. Possibly A. brownei which has been caught off the 

 west coast of Ireland and in the Chamiel at Plymouth, and which 

 presents tv\'enty pairs of tentacles might be brought into this 

 group, as an overgro^ii oceanic larva. 



A. pallida, Schneider, only measures 0-G mm., and has six 

 pairs of tentacles. It was got at Wimereaux and at Hehgoland. 

 A. metschnikoffi from the Mediterranean also has a size of 0-6 mm., 

 and possesses eight pairs of tentacles. A. sabatieri reaches a size 

 of 0-8 mm., and the tentacles number twelve pairs. The species 

 described as A. hatscheki and A, ashworthi have the same general 

 characters. This species or group of species may be said to be 



