ACTINOLOGICAL STUDIES. 309 



same genus show marked differences in this respect. The 

 brothers Dixon record that in four specimens of Bwwdes 

 thallia (1889, p. 318), one, two, three, and four oesopha- 

 geal grooves were found ; while in Bunodes verrucosa, 

 on the other hand, the whole of twenty-three speci- 

 mens examined had the normal number. I consider, 

 then, that the constant hexamerism which I find 

 obtains without exception in the specimens of Actinia 

 equina examined by me, even where variation in other 

 directions has crept in, is an interesting feature of the 

 species. 



Papers Beferred To. 



1879. Hertwig, 0. and B. Die Actinien anatomisch 

 und histologisch mit besonderer Beriicksich- 

 tigung des Nervensy stems untersucht. Jena. 

 Zeitschr., Bd. XIII., pp. 457-640, Taf. XVIL- 

 XXVI. 



1882. Hertwig, E. Eeport on the Actiniaria dredged 

 by H. M. S. "Challenger" during the years 

 1873-76. The Voyage of H.M.S. " Challenger," 

 Zoology. Vol. VI., pp. 1-136, Pis. I.-XIV. 



1888. Dixon, G. Y. Eemarks on Sagartia venusta and 



Sagartia nivea. Sci. Proc. Eoy. Dublin Soc, 

 N.S. Vol. VI., pp. 111-127. 



1889. Dixon, G. Y., and Dixon, A. F. Notes on 



Bunodes thallia, Bunodes verrucosa, and Tealia 

 crassicornis. Sci. Proc. Eoy. Dublin Soc, N.S. 

 Vol. VI., pp. 310-326, Pis. IV. and V. 

 1889. Haddon, A. C. A Eevision of the British Actiniae. 

 Part I. Sci. Trans. Eoy. Dublin Soc. 2nd 

 Series. Vol. IV., pp. 297-361, Pis. XXXI- 

 XXXVII. 



