GROMIA 



337 



spicules, &c. Similar variations to those witnessed in shell formation can be traced in the several reproductive 

 processes. The molecular reproductive elements, whether belonging to a simple cellular animal, a hermaphrodite, 

 or a bisexual individual, are, according to popular belief, homogeneous and identical. They are not really so. Each 

 animal only produces its own kind. With the physical conditions of reproduction as regards atmosphere, heat, 

 moisture, &c., practically the same, the presence of heterogeneous molecules, that is, molecules varying in 'shape' 

 properties, and powers, and variously assorted and arranged, and with potentialities all their own, becomes a necessity! 

 From homogeneous identical hving matter, only one kind of animal could possibly be obtained. 



What is true of the molecular basis of reproduction in the aggregate is equally true of the particular sarcode 

 or elementary life stuff of the Foraminifera. To obtain different structures and types even of shells requires 

 pecuUarities and special powers in the molecules of the sarcode. There is no logical escape from the beHef here 

 expressed. 



The following is the account given of gromia by Dr. Carpenter,i who devoted much attention to the subject :— 

 " In the Gromia}, some forms of which inhabit fresh waters, whilst others are marine, the sarcode body, which is 

 of essentially the same character with that of Lieberkuehnia, is enclosed in a yellowish brown membranous " test " 



Fig. 71. — Haliovnna mjviUii, 

 meters (after Wyville Thomson). 



magnified 200 dia- 



FiG. 72. — Xiphacantha murrayana, magnified 100 

 diameters. Shows symmetrical, concentric, and radiat- 

 ing arrangement of parts (after Wyville Thomson). 



of ovoidal shape, with a single round orifice of moderate size, through which the protoplasmic substance extends 

 itself from the interior through the surrounding medium. When the animal is in a state of rest the whole of this 

 is drawn within the test ; and when its activity recommences single fine processes are first put forth, which move 

 about in a groping manner imtil they find some surface to which they may attach themselves. When this attach- 

 ment has taken place new sarcode flows into them, so that they speedily increase in size ; and they then elongate 

 themselves by sending out finer ramifying processes, which, in diverging from each other, come into contact with 

 those proceeding from other stems, and, by mutual fusion, form a set of inosculations or connecting bridges 

 between the different systems of ramifications, so that the whole becomes a complicated network extending to a 

 distance of six or eight times the length of the body. This network continues to undergo incessant changes, new 

 filaments being put forth in different directions, sometimes from its margin, sometimes from the midst of its 

 ramifications, whilst others are retracted. Not unfrequently it happens that at a spot where two or more filaments 

 meet and fuse together a lamina is formed by the expansion of the viscous protoplasm that flows towards this point ; 

 and from such an expansion a new set of thread-hke processes is given off, as from the central body." 

 [ The general appearance presented by a living gromia is given at Fig. 70 (see also Plate Ixxx., Fig. 3, page 309). 



The Foraminifera have been divided into two kinds, namely (a) those with one large aperture through which 

 the pseudopodia stream and radiate, and {h) those with perforated shells which give additional outlets for the sarcode 

 in its active state. In both arrangements the sarcode behaves in exactly the same manner ; it exhibits a centri- 

 fugal and centripetal rhythmic action : in other words, it flows and streams out of the shell centrifugally in virtually 

 straight hues in a radiating manner ; the object being to secure food, fix itself, or change its locaUty. The 

 streaming of the sarcode in thread-hke pseudopodia affords the simplest and best example known of vital force 



' " Introduction to the Study of the Foraminifera." 

 VOL. I. 2 u 



