Dr. J. D. Macdonalcl on the Polycystina. 225 



Notwithstanding the evidence of excellent observers as to 

 the pseudopodia and the locomotive properties of genuine 

 Foraminifera, I can onlj say that, having from time to time 

 submitted thousands of the living animals to close inspection, 

 I have seen no evidence of the existence of pseudopodia, and 

 perfect fixity has been the rule, either by a Woad base or a 

 pedicle. Indeed the place of attachment of the latter is usu- 

 ally distinctly apparent in the dead shells. 



The echinated Globigerine forms are generally found in the 

 free state, being often taken in the towing-net with the Tha- 

 lassicollidse or amongst the ingesta of Salpce and other pelagic 

 animals. After the death of the sarcode, these little shells 

 gravitate to the bottom of the ocean, in company with the 

 siliceous frustules of Diatomacese and the crystal domes, con- 

 centric spheres, and the diverse spicular and fenestrated frame- 

 work of the Polycystina, which also enjoy a pelagic life. 

 Thus organic and sedimentary particles commingle to compose 

 incipient rocks, whose intimate structure at some remote 

 period may be studied with interest by future geologists. 



In AcantJiometra the animal sarcode is deposited centrally, 

 but at the same time superficially, around the conjoined bases 

 of the radiating spines, through the tubular axis of which 

 pseudopodial extensions of the sarcode may protrude. There 

 are, however, some pedunculated forms (such as are often to 

 be found attached to the keel of Atlanta^ the shells of Ptero- 

 poda, and other pelagic bodies) Avith exceedingly delicate and 

 imperforate spines radiating through a reddish-brown sarcode 

 mass surmounting the pedicle {AcantJiometi^a^ young?). 



Professor Miiller describes the sarcode of the Eucyrtidium 

 of Messina as an olive-brown four-lobed body occupying the 

 dome or summit of the shell, through the fenestrations of 

 which emerge fine pseudopodia like those of Actinophrys. 



Many of the free Polycystina (?) taken in the towing-net ex- 

 hibit a remarkable alliance with the Thalassicollidge. Thus 

 a sarcode body, in every particular resembling a single punc- 

 tum of the Thalassicolla imnctata of Huxley, or in some in- 

 stances two or three such bodies, were included within a more 

 or less open siliceous framework. 



The genus Dictyoclia is an example of this group, which I 

 have little doubt should be referred to the Thalassicollidas. It 

 is certain, however, that they are at present confoimded with 

 the Polycystina in the well-known fossil gatherings from 

 Oran, Barbadoes, and other places. 



Of course, where concentric shells are formed at intervals, 

 the mode of growth of the sarcode must be in all essential 



