A New AstomatOUS Ciliate, Metaphrya sagittae, gen. et 

 sp. nov., found in the Coelom of Sagitta. 



By 



Iwaji Ikeda, Rigakuhakushi. 



During a short stay, in December of 191 3, at the Misaki Marine 

 Biological Station, Dr. Yatsu kindly called my attention to a living 

 specimen of Sagitta, which contained some large ciliates in the body- 

 cavity. Upon close examination under the microscope, these were ascer- 

 tained to represent a new mouthless holotrichous form of a remarkable 

 characterization. I propose to call it Metaphrya sagittac, gen. & sp. nov. 



Owing to the transparency of the host, much of the external characters 

 of the parasites could be observed in their natural habitat. Fig. 1 re- 

 presents the surface view of one of the four largest 

 specimens in life. The body is pear-shaped, mea- 

 suring about 0.25 mm by 0.13 mm. It is nearly 

 transparent and quite colourless. The anterior end 

 is distinctly narrower than the posterior, which is 

 rather rounded. The body appears to be radially 

 symmetrical in its structural plan excepting the fact 

 that the anterior end is somewhat deflected towards 

 one side. Fine but long cilia are present, not 

 uniformly all over the body, but growing in 12 

 longitudinal shallow grooves of the body, so as to 

 form as many equidistant ciliary bands. The organism 

 is devoid of a mouth or any other external aperture ; 

 therefore, it should belong to the suborder Astomata 

 of the order Holotricha. The cytoplasm investing the body is finely 

 granular ; its differentiation into the ectoplasm and the entoplasm is in the 

 fresh state indistinct. Beneath this cytoplasmic layer there can be recog- 



Fig. I. 



Fully grown 

 Metaphrya sagititu 

 in the living state. 

 Xi8j. 



