COMPARATIVE ANATOMY OF SOME BRITISH ACTINIA. 523 



S. miniata is a much smaller anemone, S. viduata being about 50 mm. 

 long and 15 mm. broad. *S. viduata is also characterised by grey, green, 

 and brown colours instead of the lake, orange, and crimson found in 

 S. miniata. In S. viduata the warts (which Gosse called suckers) lie in 

 the upper third of the column. The cinclides open in the middle of 

 these prominences. In *S. miniata, the cinclides seem to be very few, 

 opening, as in S. viduata, in the middle of some of these prominences near 

 the oral disk. 



Arrangement of the mesenteries. 



In S. viduata, Carlgren has found a definite number of mesenteries, i.e. 

 96 pairs, including two pairs of directives, arranged in five cycles 

 thus, — 6+6+12+244-48. The last cycle is represented by mere 

 projections of tissue developed in the lowest part of the column. In 

 this species the arrangement coincides with the number and arrange- 

 ment of the tentacles which are in 6 cycles, 6+6+12+24+48+96=192, 

 I have cut sections of several specimens of S. miniata but am unable 

 to make out any definite plan of the arrangement and number of 

 mesenteries. The same difficulty has arisen in connection with other 

 members of this genus, in S. venusta, S. troglodytes, and S. nivea. 



In his paper " On the arrangement of the mesenteries in the Genus 

 Sagartia," in Proc. R.D.S., 1888, F. Dixon says that he was unable in 

 most cases to recognise a completely hexamerous arrangement of the 

 mesenteries. The only regularity seen was the correspondence of the 

 number of directives with that of the oesophageal grooves. Dixon gives the 

 number of mesenteries, etc., from three specimens collected near Dalkey 

 Island. The following data are taken from three specimens from Valentia 

 Island, probably older and larger than those examined by Dixon : — 



Specimen {a) : 20 pairs of mesenteries reaching the oesophagus, in- 

 cluding 1 pair of directives. There is 1 oesophageal groove present. 

 About 20 pairs belong to 2nd cycle and are incomplete. The 3rd 

 cycle consists of about 40 small mesenteries which penetrate only a very- 

 short distance into the coelenteron. 



Specimen (6) : This has 24 pairs of mesenteries reaching the oesophagus, 

 including 2 pairs of directives arranged in the order : 



D. 9, D. 13. 



The 2nd cycle consists of about 24 mesenteries, and the 3rd cycle of 

 about 48 ; these latter project only a short distance beyond the column 

 wall. There are 2 oesophageal grooves here. 



Specimen (c) : This showed 1 oesophageal groove and 1 pair of direc- 



