MICROSCOPIC FORMS OF ANIMAL LIFE. 



9 



Fio.283. 



lished by Dr. Wallich. The sarcode-body of this animal is incased in an 

 egg-shaped, brownish-yellow, chitinous envelope, which may attain a dia- 

 meter of from l-12th to l-10th of an inch, looking to the naked eye so 

 like the egg of a Zoophyte or the seed of an aquatic Plant, that its real 

 nature would not be suspected as long as it remains quiescent. The 

 * test ' has a single round orifice, from which, when the Animal is in a 

 state of activity, the sarcodic substance streams forth, speedily giving off 

 ramifying extensions, which, by further ramification and inosculation, 

 form a network like that of Lieberkiihnia. But the sarcode also extends 

 itself so as to form a continuous layer over the whole exterior of the ' test;' 

 and from any part of this layer fresh 

 pseudopodia may be given off. By 

 the alternate extension and contrac- 

 tion of these, minute Protophytes 

 and Protozoa are entrapped and 

 drawn into the interior of the test, 

 where their nutritive material is ex- 

 tracted and assimilated; and if the 

 ' test ' (as happens in some species) be 

 sufficiently transparent, the indiges 

 tible hard parts (such as the siliceous 

 valves of Diatoms, shown in Fig. 

 283) may be distinguished in the 

 midst of the sarcodic substance. By 

 the same agency, the Grown' a some- 

 times creeps up the sides of a glass 

 vessel. In the intervals of quies- 

 cence, on the other hand, the whole 

 sarcodic body, except a film that 

 serves for the attachment of the test, 

 is withdrawn into its interior. 



398. Another example of the Re- 

 ticularian group la afforded by the 

 curious little Microgromia socialis 

 (Fig. 284), first discovered by Mr. 

 Archer, and further investigated with 

 great care by Hertwig; 1 which has 

 the curious habit of uniting with 

 neighboring individuals, by the fus- 

 ion of the pseudopodia, into a com- 

 mon * colony;' the individuals some- 

 times remaining at a distance from 

 one another as at A, but sometimes 

 aggregating themselves into compact 

 masses as at B. The nearly globular 

 thin calcareous shell is prolonged into 

 a short neck having a circular orifice, 

 from which the sarcode-body extends itself, giving off very slender pseudo- 

 podia which radiate in all directions. A distinct nucleus can be seen in 

 the deepest part of the cavity; while a contractile vesicle lies imbedded in 

 the sarcodic substance nearer the mouth. Multiplication by duplicative 

 subdivision has been distinctly observed in this type; but with a peculiar 



Gromia oviformis, with its pseudopodia 

 extended. 



1 'Ueber Microgromia;' in " Archiv fur Mikr. Anat.," Bd. x., Supplement. 



