ROTIFER-K 440 



have the power of retracting itself perfectly within the 

 hyaline membrane. The hyaline membrane is at certain 

 periods of the year so very translucent that it cannot be 

 made out ; later in the season it is found studded with -para- 

 sitic desmids, when its gelatinous form is readily seen. The 

 body is ovoid or cup-shaped, and the mouth is surrounded 

 by long cilia, which are always in rapid motion. When 

 the animal becomes alarmed it instantly retracts, and then 

 has the appearance of a small round ball. On the frontal 

 plane four thickish conical erect papillie are placed, each fur- 

 nished with one or more spines or setie ; very near their 

 base, rather behind, and between the division of the 

 ciliary band, are the very minute visual organs. The 

 jaws, it is said, are furnished with teeth, but these we 

 have not been able to make out, chieflv owins: to their 

 disposition to break up in a short time after being placed 

 in confinement. The stomach is oval, and two ovoid 

 bodies are observed near the termination of the oesophagus ; 

 below these the ova-sack encloses a single ovum of a dark 

 colour. The ovum is surrounded by spinous processes, or 

 cilia, and when first thrown off it lodges for a time in the 

 hyaline membrane ; but, when set free, moves slowly 

 about. A few minutes after being placed in the glass-cell 

 the colony become uneasy, break themselves off one after 

 the other, and swim away to die. They were formerly 

 classed among Volvocinece, but bear no resemblance to 

 them, except in their roll through the water ; and are 

 more properly |)laced among the Kotifers. 



Acineta tuberosa, Plate 111. No. 68. — The researches of 

 Stein are said to prove that the several members of this 

 family are simply a developmental phase of Vorticellina ; 

 this view, however, is controverted by Lachmann, Cla- 

 parcde, and others who have witnessed the reproduction of 

 Acinetce from parent forms. A. tuberosa has a triangular- 

 uhaped body and three obtuse tubercles or horn?:, each 

 fainishe<l with tentacula. Many other forms of this 

 genus are well known ; but, notwithstanding the diversitv 

 in construction, Stein declares their tubular ramified pro- 

 cesses to be morphologically and physiologically identical 

 with ordinary tentacula. Vaginicola crysiallina he puts 

 forward as one of the best illustrations to be obtained of 



G G 



