1886.] 



MICKOSCOPICAL JO[JRNAL. 



107 



protection of these frail shells from 

 dust and accident a cover is neces- 

 sary, and it must be removable in 

 order to get access to the specimen 

 when it is desired to transfer it. This 

 cover is supplied by curtain-rings, ce- 

 mented one upon the other and capped 

 with thin glass, and it is secured by 

 small tacks driven just far enough 

 apart and just deep enovigh so that 

 the heads will catch in the groove 

 between the rings. The cover is thus 

 easily removed and replaced. For ex- 

 hibition purposes, and for permanent 

 preservation and reference as well, 

 cardboard disks have been prepared. 

 The specimens are planted in succes- 

 sion, as near the circumference as pos- 

 sible, and the covers fitted as on the 

 single slides.* This cardboard disk 

 is designed to rotate on a pivot sup- 

 ported by the upper stage plate of the 

 microscope, and by means of this ro- 

 tation each object in the series may 

 be brought, in succession, into the 

 field. The dropping of a light spring 

 into a notch on the edge of the disk 

 indicates to the observer when the 

 ol)ject is in proper position. The 

 mechanical stage movements give 

 control of the object as if it were 

 on an ordinary slide. In the collec- 

 tion before you. one disk has been 

 devoted to each family. From each 

 of these have been selected the speci- 

 mens on the disk under the micro- 

 scope, to which your attention is 

 specially directed. Whenever neces- 

 sary to identification or to elucidation 

 of structure, sections of the shells have 

 been made, and the sections mounted 

 on the same slide with the entire speci- 

 mens. Some few very thin or delicate 

 specimens have been mounted in bal- 

 sam, as it brings out more distinctly 

 the peculiarities of structure. These 

 are placed on the disks for examina- 

 tion by reflected light ; they may be 

 removed and placed on a glass slip 

 and viewed by transmitted light, if 

 desired. 



It may not be altogether amiss, 

 even in a society of biologists, to re- 



* Rotary Object Carrier, vol. vi, p. 204. 



call a few facts regarding this group 

 of animals, apologizing to those who 

 have made the subject a study for the 

 trite remarks. 



The foraminifera comprise a group 

 of aniinals belonging to the sub-king- 

 dom Protozoa, Class Rhizopoda. 

 They stand nearly at the foot of the 

 list in the classification of animal or- 

 ganisms by reason of the extreme 

 simplicity of their structure, which 

 consists of a minute bit of protoplas- 

 mic substance without differentiation 

 of endosarc and ectosarc, without 

 contractile vesicles, and imtil recently 

 believed to be without even a nucleus. 

 Like the other rhizopods they possess 

 the power of thrusting out portions 

 of the body substance or pseudopodia. 

 which, when retracted, lose them- 

 selves again in the body mass. The 

 character of these pseudopodia has 

 led Prof. Carpenter to divide the 

 rhizopoda into three classes: i. Lo- 

 bosa, of which Ama'ba is the type, 

 the pseudopodia of which are blunt 

 or irregularly club-shaped, and show 

 no disposition to unite with one an- 

 other when the}- come into contact ; 

 2. Reticulosa, to which class belong 

 the foraminifera, whose pseudopodia. 

 projected in fine threads, unite when- 

 ever thev come into contact, forming 

 a network ; and, 3. Radiolaria, of 

 which Actiiiophrys is the type. The 

 pseudopodia in this instance are pro- 

 jected radially and do not unite. 



But little is known of the life his- 

 tory of these minute and simple ani- 

 mals. Their ordinary mode of mul- 

 tiplication is undoubtedly by sub- 

 division or fission. But there seems 

 to be some definite limit to the possi- 

 bilities of that process, and it is 

 probable that some form of conjuga- 

 tion and encysting process will ulti- 

 mately be discovered. Their mode 

 of nourishment is supposed to be by 

 the absorption of the organic matter 

 in solution in the sea-water, since 

 the pores of the shell are, in most 

 instances, toQ small (the largest being 

 about g^o'nn ^f ^" "'^^^'' i'"" tlii*i"eter) 

 to allow the introduction of any solid 



