728 ORDER PERITRICHA. 



Pyxicola socialis, Gruber sp. Pl. XL. Figs. 16, 30, and 31. 



Lorica ovate or urceolate, produced anteriorly into a narrower distally 

 expanded neck, the central region ornamented with three distinct grooves 

 or annulations ; pedicle equalling or slightly exceeding the length of the 

 lorica, straight or irregularly curved ; body extending but slightly beyond 

 the aperture of the lorica ; the oral side of the peristome bearing a circular 

 indurated operculum of the same colour and consistence as the lorica. 

 Length of lorica 1-250". 



Hab. — Salt water, social ; colour of lorica dark brown in adult 

 examples, yellow or colourless in younger specimens. 



This species, originally described by Dr. August Gruber,* in company with 

 TJmricoIa operculata and other interesting forms, under the title of Cothuniia socialis, 

 is appropriately named in allusion to its eminently gregarious habits. While isolated 

 specimens are met with^ it more usually happens that a single primary lorica, as 

 shown at PI. XL. Fig. 30, gives support to three or four more, producing in the 

 aggregate a pseudo-compound colony-stock remarkably suggestive of the compound 

 " polythecia " of the flagellate genera Dinohryon, Stylobryon, and Polycpca, described 

 in the preceding volume. In other words, as Dr. Gruber suggests, " the species 

 affords an example of the least modified form of a compound animal or ' stock ' ; the 

 connection of the various persons forming it being of the loosest description." 

 According to its discoverer, there is developed in this type, on the inner edge of the 

 peristome on the oral side, a very delicate funnel-shaped or collar-like membrane, iden- 

 tical, he says, with the structure usually described as a brisde-like cilium {soie de Lach- 

 manii). This membrane, which is evidently homologous with the collar-like mem- 

 brane of Operciilaria, bounds the mouth externally as an outwardly sloping wall, 

 being highest immediately opposite this orifice, and gradually sloping away on either 

 side. Particles of food hurled against it by the action of the cilia of the disc are at 

 once swept into the oral entrance, while those missing it are whirled away from the 

 animal. 



It appears desirable to identify with Pyxicola socialis the somewhat nondescript 

 organism, half Rotifer and half Infusorium, figured and described by Mr. John 

 Davies in the ' Journal of the Royal Microscopical Society' for October 1879, under 

 the tide of Cothurnia corriigata. The contour of the lorica agrees entirely with that 

 of Gruber's species, except that two cusp-like processes would appear, in accordance 

 with the figures given, to be usually developed at the posterior extremity. Mr. Davies' 

 summary of the morphological characters of the contained animalcule, as shown in 

 the following quotation, serve no other purpose beyond that of revealing a surprising 

 lack of acquaintance with even the most elementary details of the organic beings 

 among which he would allocate the subject of his discovery : — 



"The cephalic extremity of the animal (Rotifer) when extended is of an oval form, hardly as 

 long or as broad as the aperture of the lorica. The head is furnished with two strong cilia, or more 

 properly speaking, setre, which are forked to about half their length, a follicle being observed at their 

 base. The thread-like appendages (setae ?) move with a spasmodic jerk, and are very irregular in 

 their action. They may be probably covered with a glutinous matter, as they are frequently observed 

 to bend towards the central vortex, possibly to deposit particles that have adhered to them. At the 

 end of the thoracic tube is what seemed to be a mastax. In this part of the animal are situated 

 two contractile vesicles, one on either side of the jaws. No eyes were apparent. Towards the 

 posterior extremity is a light coloured and rather large vessel, which I believe to be the anus. The 

 footstalk has, I believe, a central cord as in Vorticella, but I am not certain on this point. It does 

 not at any time contract its stalk ; in fact, it exhibits no motion in this part of its organization." 



A serious analysis of the foregoing diagnosis will not be attempted, but it may 

 be suggested that the so-called forked sette or thread-like appendages therein 



' Zeitschrift fiir Wissenschaftliche Zoologic,' Bd. xxxiii., 1879. 



