ON ANTHURA GRACILIS (MONTAGU). 



239 



A very interesting point in this species is the presence of statocysts 

 in both male and female. I am indebted to Dr. Caiman for drawing my 

 attention to the question of the existence of these organs in the 

 Anthuridse ; to Dr. A. Thienemann for sending me some of the actual 

 specimens referred to in his paper {Zool. Anz., Vol. XXVI, pp. 406-410) ; 

 and to Dr. Allen for his kindness in sectioning specimens of both 

 Cyathura carmata and AntJiura gracilis. 



The species, of which the statocysts are so fully described by Thiene- 

 mann, proved to be Cyathura carinata (Norman and Stebbing, Trails. 

 Zool. Soc, Vol. XII, p. 124) as suggested by Gurney {Trans. Norfolk 



Anthura gracilis. Fio. 4. — Horizontal section, upper part of statocyst on the right side, 



showing duct, X 100. 

 Fig. 5. — Horizontal section, lower part of statocyst on the left side, 

 showing the crystalline bodies of the statolith, x 435. 

 d, duct ; m, muscle ; si, statolith ; i', vesicle. 



Nat. Soc, Vol. VIII, p. 433). I have figured the telson of both species 

 for comparison. 



It will be seen that the general structure of the statocysts is exactly 

 the same in both genera, but the details naturally vary a little. It is 

 impossible to see these organs in specimens preserved in the usual way. 

 Dr. Thienemann, in reply to a question as to whether they were to be 

 observed in the living animal, said : " So viel ich weiss, warendie Organe 

 am Lebenden nicht zu sehen ; dagegen waren Sie sehr deutlich bei Auf- 

 hellung mit Nelkenol, Kreosot oder Zylol." Dr. Thienemann adds the 

 interesting note that in two species of another genus of the Antkuridce 

 examined by him, viz. Calathura hrachiata Stimps, and C. norvegica 

 G. 0. Sars, in Bergen Museum, no statocysts were found. 



Each statocyst consists of an oval vesicle, lying embedded in the 



