APPENDIX. 86 1 



the contractile vesicle contracts quickly every thirty seconds and gives an impulsive 

 acceleration of the forward motion, or if at rest, causes at systole a forward movement 

 of the body for one-quarter of its length. 



Stentor amethystinus, Leidy.* Body trumpet-shaped when extended, oval 

 when contracted, somewhat resembling S. igneus, existing in attached groups ; endo- 

 plasm containing an abundance of chlorophyll, but the exterior structure invariably 

 of a distinct lilac or amethystine colour ; endoplast ovate. Length, when extended, 

 1-40." HAB. Fresh water. 



The larger size of this animalcule serves to distinguish it from Stentor igneus, 

 which is also reported by Stein to sometimes assume a brownish or lilac-coloured in 

 place of the more normal scarlet hue. 



Sparotricha vexillifer, Entz. This title is bestowed by Entzf on a form 

 obtained by him from the salt-pans of Hungary, and which he describes as differing 

 from its near ally Stichotricha in the circumstances that the peristomal cilia are 

 disposed in a continuous banner-like series, in the irregularity of the arrangement 

 of the other cilia, and in its incapacity to rapidly change its form. The absence of 

 frontal styles distinguishes it, on the other hand, from the genus Uroleptus. Two 

 other new forms, Litonotus grandis and Ervilia salina, were obtained by Entz 

 from the same locality, but the author has not so far been able to obtain access to 

 their original description. 



Drepanostomum pectinatum, Ehr. This proposed new generic and specific 

 type is very vaguely described by Ehrenberg J as most nearly resembling Vaginicola, 

 but having in place of the ordinary ciliary disk a slender flattened anterior process, 

 the two extremities of which bear vibratile cilia, the chamber-like centre, presumably 

 the pharyngeal cleft, being also ciliate. 



Opercularia arenicola, Greef. Colony-stock usually consisting of two zooids 

 only, which are situated close to each other at the extremity of a very short stiff 

 pedicle ; bodies oval, pointed at the extremities ; the peristome and ciliary disk very 

 narrow; endoplast cord-like. Length of bodies 1-300". HAB. Bog water. 



GENUS Arachnella, S. K. Dim. of Gr. arachne, spider. Here substituted by 

 the author in place of Arachnidium, Vol. II. p. 637, preoccupied by T. H. Hincks 

 ('Ann. Nat. Hist.,' Sept. 1877) for the distinction of a genus of Polyzoa. 



Pulsatella convolutse, Geddes. The foregoing title is conferred by Mr. Patrick 

 Geddes|[ on some curious cells, apparently independent organisms, observed by 

 him to occur in large quantities within the mesoderm of the marine Planarian 

 Convoluta Schuhii. The cells are a little smaller than the red blood-corpuscles of 

 the frog, are nearly in the form of a slightly curved pear, and have a large central 

 vacuole filled with fluid. On the wall of this cavity and towards the more convex 

 side of the cell, almost parallel with its principal axis, there is a row of homoge- 

 neous transparent fibrillae, which are inserted at their upper and lower extremities in 

 the ordinary protoplasm of which the other parts of the cell is composed. If these 

 cells are examined free in sea-water, it is seen that they are in a state of rhythmical 

 contraction, the rapidity and vigour of which are equally surprising, the most active 

 pulsating from 100 to 180 times per minute ; each time the principal axis becomes 

 more strongly curved and the cell shorter and broader. This change of form 

 depends exclusively on the contraction of the inner fibres, the other parts of the 

 cell remaining quite passive. The movements of the cell soon begin to slacken, 

 become irregular and feeble, finally cease, and the cell bursts. Its protoplasm soon 

 perishes, but the fibres resist for a longer time the action of the water, and even 



* ' Proc. Acad. Nat. Sci. Philadelphia.' 1880. 



t " Ueber einige Infusorien des Salzteiches zu Szamosfalva." ' Termeszetrazii fiizetek,' vol. iii. 

 219. 



\ 'Bonplandia,' 1861. 



" Protozoenfauna der Moos," ' Marburger Sitzungsbericht,' S. 22, 1873. 

 || 'Comptes Rendus,' xciii. (iS8i) ; also Abstract in 'Journ. Roy. Micr. Soc.,' April 1882. 



