162 DESCRIPTION OF [Tvli/gastiica. 



fail to have been observed so soon as any of this green water was 

 examined under the microscope. 



Wherever these creatures exist in great quantities, multitudes of 

 them die ; their bodies, and the envelopes cast off by the living ones, 

 are decomposed, gaseous matter is generated, which adhering, causes 

 them to rise to the sui'face of the water, forming a green stratum 

 upon it. Although the animalcules, and their coverings, when in 

 this state, somewhat resemble Uhacece, yet are they easily distin- 

 guishable from them by the red speck or eye, wliich is retained for 

 a considerable time after death, and the new bodies may be seen 

 connected together by means of an intervening membrane, formed 

 of dead colourless Infusoria, and the remains of loricae. Size l-550th. 



Genus Spha^ieosiiia. The rudder Animalcules. — The distinguishing 

 features of this genus arc its being deficient of the tail, but possessing 

 the eye, and a simple filiform rudder-like proboscis. Its method 

 of self-di\dding is difterent from that of any of the preceding genera, 

 inasmuch as it occiu^s imequally within the envelope, when young- 

 clusters are formed at once fi'om the parent ones. This genus differs, 

 then, from Pandorina, in having the eye ; from Eudorina, by its un- 

 equal mode of self-di-vdsion ; and, from Volvox, by its simple pro- 

 boscis. Self-di\ision in these creatures takes place in the longitudinal 

 ■direction, commenciug in parallel jjlanes, so that lamina are produced 

 as with the Gonium. Since, according to Dujardin, but one filament 

 exists in Volvox, tliis genus should be set aside as indistinguishable 

 from the latter. 



S. volvox, — Body composed of pale green corpuscles, of nearly a 

 globular shape, enveloped in a lorica of the mantle form. Eye bright 

 red. The cluster resembles a great ball of animalcules, containing 

 small compressed clusters within it. Fig. 49 represents a portion of 

 the tunic or lorica, highly magnified, so as to shew the difierent forms 

 of the creatures located within it ; thus, three single animalcules, 

 one mulberry- shaped cluster, and one oblong group may be observed 

 within that portion of lorica. Figure 48 represents a large spherical 

 cluster. Found in considerable numbers in company with the Volvox 

 (jlohator, and often attains its size. Sometimes foimd by itself. 



Genus Volvox. The ylohe Animalcules. — The genus Volvox, which 



