POLYGASTRIA. 



On closer inspection it is seen that all the 

 Monads, which are placed at regular distances, 

 communicate with each other by delicate threads, 

 which form a kind of reticulation in the com- 

 mon gelatinous skin-like integument of the 

 compound body, or polypary, as it might be 

 aptly called, out of which the contained ani- 

 malcules only protrude their proboscides either 

 in search of food or to row the general mass 

 along. 



It is easy to prove by flattening the Volvox 

 between two plates of glass that its interior is 

 only filled with water, in which sometimes 

 there may be observed smaller volvoces swim- 

 ming about, the products of the propagation of 

 some of the constituent animalcules. These 

 are not solitary young ones, but may already be 

 seen to be composed of numerous individuals, 

 formed by the continual division of the original 

 from which they sprang. 



Another mode of reproduction is by the 

 laceration or division of the globe itself. When 

 this takes place, either for the escape of the 

 included Volvoces generated within, or from 

 any other cause, the component Monads im- 

 mediately prepare to leave their domiciles, and 

 the individual animalcules become separatee! 

 by the dissolution of the inter-communicating 

 threads ; they then, by little and little, extri- 

 cate themselves from the common gelatinous 

 envelope, and creep out to commence an inde- 

 pendent existence. The gelatinous polypary of 

 the original Volvox in consequence speedily 

 loses all its green spots ; and as every little point 

 is active, moving its proboscis freely when it 

 leaves the common globe, it may fairly be 

 concluded that they have a power of indepen- 

 dent existence, and that each is able to begin 

 the construction of another compound Volvox 

 as wonderful as that we have been considering. 



The developement of the embryo of the 

 Volvox is represented in 11, 12, 13, fg. 1. 

 In II, Jig. I, is represented the simplest con- 

 dition of a granular mass containing a clear 

 central spot, which in the course of a few hours 

 assumes the condition represented in 12, Jig. 

 1, by undergoing an imperfect spontaneous 

 division. By a continued repetition of this 

 division it becomes at last broken up, until it 

 has the appearance shewn in 13, Jig. 1. The 

 component vesicles still go on subdividing, 

 until it assumes the appearance of a single 

 perfect Monadine possessed of two proboscides, 

 eye-spots, &c. By a further developement it 

 constructs for itself an external envelope, which 

 has the appearance of a white ring surrounding 

 the central nucleus. 



Wonderful as is the organisation of the last 

 family, it would probably not be more so than 

 that of the Vibriomdae, was it in our power to 

 display their internal economy in an equally 

 satisfactory manner; but such is the extreme 

 minuteness of all the members of the family, 

 that even to Ehrenberg this seemed a hopeless 

 wish. The Vibrionidse present themselves under 

 the microscope as thread-like bodies of in- 

 describable tenuity, worming their way in 

 countless thousands through the drop of water 

 in which they live, and presenting themselves 



in different shapes, which have been classified 

 as belonging to five distinct genera, named as 

 follows : The first, Bacterittm, contains those 

 forms which exhibit the appearance of stiff- 

 jointed filaments. In the second, Vibrio, the 



1, 2, 3. Vibrio subtilis. 4. Vibrio rugula. 5. Vibrio 

 rngula more highly magnified. 6. Closterium. monili- 

 ferum. 7. Closterium turgidum. 



a, a, a, three large aggregations of living cor- 

 puscles; x, x, the locomotive papillae; o, o, open- 

 ings in the shell. 



creatures resemble minute chains, which seem 

 to be as soft and flexible as the body of a 

 serpent, although so exceedingly minute that 

 some species have been calculated to be not 

 more than the 300th of a line long, and the 

 3000th of a line in thickness. 



The animalcules in some genera assume the 

 appearance of tortuous chains or flexible spiral 

 threads. In Spirillum the body seems rolled 

 into a stiff spiral cylinder, and in Spirodiscus 

 it is arranged in a kind of disc. 



On examining these little beings while alive, 

 little doubt can be entertained that they belong 

 to the animal series of creation : the manner in 

 which they obviously direct their course at will, 

 and the facility with which all their movements 

 are performed, have caused them to be recog- 

 nised as animals by all observers. It is, how- 

 ever, to Ehrenberg that we are indebted for the 

 discovery of their real nature. From his ob- 

 servations we learn that these living filaments, 

 minute as they are, are not single animals, 

 but chains composed of numerous associated 

 individuals produced from each other by spon- 

 taneous fissure. There even seems to be reason 

 to sus'pect that their internal structure is in 

 some degree allied to that of the Monadines ; 

 at least in one species, Bacterium triloculnrc, 

 Ehrenberg perceived a proboscidiform mouth 

 similar to that possessed by the Monadines of 

 Volvox. 



The peculiar forms assumed by the different 

 genera of Vibrionidae seem to depend upon the 

 character of the fissiparous division by which 

 the whole chain is produced, the compound 

 body remaining straight or becoming thrown 

 into spiral folds as the division is equably or 

 unequably carried on. 



The snake-like movements of the true Vibrios 

 during their progress in the water, Ehrenberg 

 conceived to be produced by a power of con- 

 tracting forcibly, that resides in the individual 



