OF THE VORTICELLINA. 



580 



seems nothing to sufficiently distinguish 

 it from the preceding spacies ; for the 

 bhiish hue of the granules cannot be 

 admitted as a characteristic. Even the 

 difference in dimension is no satisfactory 

 indication of a distinct species ; for the 

 smaller animalcule may be but a younger 

 specimen of the larger. 



S. pohjmorplnis (xxix. 7) resembles 

 the preceding in form. Granules of a 

 beautifid green colour; nucleus articu- 

 lated and chain-like ; lateral crest in- 

 distinct; frontal wreath of cilia inter- 

 rupted. This species will not receive 

 indigo readily. Transverse self-division 

 observed. Upon stones, decayed sticks, 

 and leaves, in standing water. 1-120" to 

 1-24". 



Lachmann {A. N. H. 1857, xix. p. 

 225) seems to intimate that this species 

 is equivalent to ♦S'. Mulleri and S. Rceselii. 

 Both in this species and in *S'. ccendeus 

 Eckhard has described reproduction by 

 internal germs or embr^'os. Between the 

 cilia, disposed in spiral series, single long 

 hairs, similar to those of many Turbel- 

 laria, are found, according to the testi- 

 mony of Lachmann. 



S. iyneus. — Less than the preceding; 

 granules yeUowish-green ; smface bright 

 yellow or vermilion ; nucleus spherical ; 

 lateral crest absent ; frontal ^\Teath of 

 cilia interrupted. Found by Ehrenberg 

 upon the water- violet {Hottonia palus- 

 : tris). 1-72". 



I S. 7iiger (Vorticella nigra, M.). — Small, 



! of a dark browmish-yellow or blackish 



j colour ; granules olive-coloured ; nucleus 



spherical ; lateral crest absent ; frontal 



j wreath of cilia continuous. This species 



! is often so abundant that it colours large 



I pools, in turfy hollows, of a dark blackish 



I hue, resembling an infusion of coffee. 



The sv^-imming movement of this species 



is readily seen (as in the others) with 



the naked eye. 1-96". 



S. castaneus (Wright). — K species 

 named in a letter to us by Dr. Wright, 

 of which the only particulars given are 

 that it is of a dark chestnut colour, and 

 that it selects the tops of the stems of 

 Myriophyllum as its home, and glues all 

 the young leaflets together with a baU 

 of jelly, within which a crowd of zooids 

 is imbedded. 



Genus TRICHODINA.— Yorticellina destitute both of tail and pedicle, 

 distinguished from the preceding genus by the general smface of the body 

 being destitute of cilia. They possess a vibrating wreath of cilia anteriorly, 

 on one side of which is a simple, not spiral oral opening. They are mostly 

 disc-shaped or conical. T. Pediculus has the posterior end abruptly trun- 

 cated like the front, and also surrounded with a wreath of curved setae, which 

 it employs when crawling, in the manner of feet. In T. tentaculata there is a 

 kind of proboscis. Coloiu-ed food is received by T. Pediculus and T. GrandineHa. 

 A kidney-shaped nucleus is seen in T. Pediculus. Many species live parasitic 

 on freshwater MoUusca, or Zoophytes ; but others have been found free in 

 sea-water. 



This description by Ehrenberg conveys a very imperfect conception of the 

 real structure and appearance of Tricliodina. The following account and 

 figures from Stein will, however, supply its deficiencies : — " The genus Triclio- 

 dina consists of naked and highly contractile animalcules, subject to very con- 

 siderable variations of form in the direction of the long axis. Their usual 

 figure is that of a tiTincated cone, much and suddenly distended posteriorly, 

 and surmounted at their wider extremity by a wreath of cilia, which corre- 

 sponds with the posterior ciliary wreath in other VorticeUina. The other, 

 abruptly truncate extremity is furnished with an apparatus of hooks (XXIX. 

 15), whereby the animal can attach itself to other bodies. The mouth is 

 circular, and placed on one side of the body, at a greater or less distance from 

 the anterior extremity ; it is furnished with a special zone of cilia to aid in 

 the introduction of the alimentary particles." (It is, however, not circular, 

 but a spii^al fringe of cilia, as Dujardin stated.) The genus Trichodina (Ehr.) 

 agrees in the main with Urceolaria (Duj.). 



Of the several species enumerated by Ehrenberg, Stein asserts that two 

 only are admissible, that the other three are foreign to the genus, and very 



