8 14 ORDER TENTACULIFERA-SUCTORIA. 



The species is to be distinguished from P, cothurjiata, which it most closely 

 resembles, by the great proportional thickness of the foot-stalk, and the 

 protuberance on the frontal margin of the body. Zenker, who has recently studied 

 its development, reports that the free-swimming embryos exhibit a holotrichous 

 plan of ciliation. These embryos, after attachment, develop at first only a single 

 terminal or axial suctorial tentacle, which thus conveys to them a close resemblance 

 to the permanently mono-tentaculate genus Rhynchcia. Claparede and Lachmann, 

 who have referred this type to the present genus, indicate in their drawings the 

 production of an embryo by internal gemmation, which would seem, however, to 

 be ciliated on one only of its lateral surfaces ; preparatory to its liberation a 

 fissure-like aperture was observed to be developed in the wall of the parent body, 

 similar to that which has been subsequently observed by Biitschli and Wrzesniowski 

 oi Fodophrya qiiadripartita and Dend7'ocometes paradoxus. 



Podophrya libera, Perty. 



Body spherical; tentacles numerous, distinctly capitate, distributed 

 throughout the peripheral surface, their length, when extended, equalling 

 three or four times the diameter of the body ; pedicle slender, its length 

 equal to or slightly exceeding the width of the body; zooids often detached 

 and freely motile. Diameter of body 1-300." Hab. — Pond water. 



This species, originally described by Perty, in its detached or free condition 

 only, has more recently been rediscovered by E. Maupas in the neighbourhood of 

 Algeria. This last-named investigator, being unable at the time to refer to Perty's 

 work, regarded it as a variety only of Podophrya Jixa, and figured and described it 

 under the title oi Podophrya fixa var. Algericnsis* but has since f fully recognized its 

 claims for recognition as an independent species. This is more especially manifested 

 by the much greater relative length of the tentaculate appendages and the tendency 

 of the animalcules to abandon their stalks and lead a free roving life after the manner 

 of a SphcBrophtya. It was observed by Maupas that, pending the transformation 

 from the fixed to the free-swimming state, the tentacles are withdrawn into the 

 substance of the parenchyma and become entirely obliterated, the body then 

 becomes elongate, and the cuticular surface more or less completely clothed with 

 fine vibratile cilia. In this condition the animalcule detaches itself and moves 

 freely in the water until, finding a locality more suited to its wants, it again fixes 

 itself by the posterior extremity. Suctorial tentacles are now protruded as 

 formerly from the inner parenchyma, the cilia are reabsorbed into the cuticular 

 layer, and the animalcule l3ecomes indistinguishable from its pristine characteristic 

 state. In addition to the motile condition just described, it not unfrequently 

 happens that Podophrya libera detaches itself from its pedicle without the develop- 

 ment of cilia, and creeps from place to place with the assistance of its adhesive 

 tentacles. 



Podophrya cylindrica, Perty. Pl. XLVIII. Fig. 20. 



Body elongate-cylindrical, about four times as long as broad, mounted 

 on a short slender pedicle ; tentacles distinctly capitate, developed irregu- 

 larly from the distal extremity of the body only ; endoplast elongate 

 ovate, subcentral; contractile vesicles not observed. Length 1-250". 



Hab. — Fresh water, on Lemna. 



This species, originally found in Switzerland and figured and described by 

 Perty, has been recently rediscovered among Lem?ice in the neighbourhood of St. 

 Petersburg by C. von Mereschkowsky. 



* ' Archives de Zoologie Experimentale, torn, iv., 1876. t Ibid., torn, ix., 1881. 



