SCIENCE-GOSSIP. 



39 



This animal occurs in vegetable infusions, and is 

 not uncommon in putrid ditch-water. 



Sub-Order Dimastiga. 



Family Heteromitidae, "Animalcules naked, 

 free-swimming or temporarily attached. The more 

 anterior appendage, ' tractellum,' locomotive and 

 vibratile; the posterior one, ' gubemaculum,' 

 usually trailing and adherent ; no distinct oral 

 aperture." 



Heteromita ovata Dujardin. — The body of this 

 animal is ovate, becoming rather narrower towards 

 the anterior. At this end the two flagella, 

 which form the chief characteristic of the genus, 

 are situated. One of these is terminal in origin, 

 the other arises somewhat posterior to it, on the 

 ventral surface. The former is called the trac- 

 tellum, for by its vibrations the animal is drawn 

 along. The other is called the gubernaculum, or 

 rudder ; by it the animal is steered and kept 

 steady when swimming, and it is anchored by it 

 when it comes to rest on some object. In H. ovata 

 the tractellum is slender, and about three times 

 the length of the body ; the gubernaculum is a 

 trifle longer, and much thicker. The surface of 

 this animal is smooth. The internal protoplasm is 

 granular, and contains an anteriorly situated con- 

 tractile vacuole. The length is 27 to 35 microns. 



This species may be met with among aquatic 

 plants, in river, stream, pond, or ditch-water. 



Heteromita globosa Stein. — The body of this 

 animal is somewhat variable in shape; it is 

 usually spheroidal or ellipsoidal. The surface is 

 coarsely granulate. The flagella are arranged as 

 in H. ovata; they are almost equal in the 

 length and thickness and are two or three times 

 the length of the body. A single contractile 

 vacuole is present, which is situated close to the 

 centre of the right lateral border. The nucleus is 

 spherical and is placed on the median line towards 



Fig. 18. — Heteromita globosa ( x 600). 



the anterior end. The length of the body is from 



to 25 microns. 



This animal lives in pond-water, and for diet 

 appears to prefer decaying animal matter. Saville 

 Kent came upon a crowd of them which were 

 having a dinner party in the carapace of a dead 

 rotifer. They seemed to consume the delicious 

 contents of this with great gusto, figuratively 

 speaking, even with enjoyment. 



Family Bikoecidae. " Animalcules sedentary, 

 ovate, or pyriform, with a usually more or less 

 projecting anterior lip-like prominence, solitary or 

 colonially associated, secreting separate horny 

 sheaths or loricae, which are mostly stalked ; flagella 

 terminal, two in number, one long and one short ; 

 parenchyma transparent ; no distinct oral aperture ; 

 endoplast and one or more contractile vacuoles 

 usually conspicuous ; increasing by transverse 

 subdivision and by the separation of the body 

 into a mass of sporular elements. Inhabiting 

 fresh and salt water." 



Bicosoeca lacustris James Clark. — The body of 

 this animal is ovate, and from its anterior end a 

 lip-like process projects. It lives in a horny lorica 

 and is attached to the bottom of this by a con- 

 tractile thread. It bears two flagella, one long and 

 more or less conspicuous and the other short and 

 hard to see. When the animal contracts into its 

 sheath, the longer fiagellum' becomes rolled up 

 into a spiral coil. Two or three contractile 



Fig. 19. — Bicosoeca lacustris ( x 750). 



(i) Expanded ; (2) contracted ; (3) an empty lorica of tlie 

 typical shape. 



vacuoles are placed near the hinder end. More or 

 less in the centre of thebody a spherical nucleus may 

 be seen. The lorica is typically ovate, the widest 

 part being near the posterior, but I have met with 

 a variety in which the reverse was the case, and 

 this is here figured. It is supported on a pedicle 

 about equal to it in length. The length of the 

 lorica is about 10 microns. 



This animal is abundant and widely distributed, 

 and lives in pond-water. 



Dallinger and Drysdale have made careful 

 observations of the life-histories of certain of the 

 Pantostomata, but as the species which they 

 investigated occur for the most part in artificial 

 cultures (such as cod-fish-head tea in an advanced 

 state of decomposition) they hardly come within 

 the limits of an article which is engaged only 

 on natural habitats. As, however, there is no 

 particular reason to suppose that the "Infusoria of 

 the field " have life-histories very different to those 

 of the more domesticated animals of Dallinger and 

 Drysdale, it would not, perhaps, be entirely out of 



