266 Mr. J. D. Macdonald on the Alimentary Matter of the Salpse. 



The accompanying figures (PI. VII.), which might be increased 

 ad infinitum, sufficiently illustrate the character of the little bodies 

 above noticed as occurring in the alimentary matter of Salpcs. 



The Diatomacese appear to embrace many new genera, but 

 some recent. 



GallionellcB (b), Naviculce (c), and forms allied to Pixidium (d) 

 will be readily recognized. The latter are composed of two 

 valves. At fig. 1 (n) the separation of these valves is repre- 

 sented; but, from the want of symmetry exhibited by them, 

 it would seem as though each pair originally formed one quarter 

 of a quadrate body, dividing by crucial fission into four distinct 

 portions. 



Fig. 3 (d) is a simpler and more symmetrical form, with its 

 soft contents remaining. 



In fig. 3 (d), which is rather imperfect, the radiating ribs are 

 beautifully branched and reticulated. 



It is rather remarkable that the minute bivalves (fig. e) were 

 generally found with the soft parts little changed, and the uni- 

 valves (f) empty, as though the animals had been digested out 

 of their shells. 



The Foraminifer with long silky hair-like processes is de- 

 serving of particular observation. It is the species most usually 

 taken at the surface of the ocean. One or two other forms with 

 minute spherical gemmules are figured in the neighbourhood. 



It appears to be much easier to establish a line of demarcation 

 between the Desmidiese and Diatomacese than between the latter 

 and the Foraminifera. 



With all our opportunities of observing living Foraminifera 

 in the South-western Pacific, where they abound in the most 

 diversified forms, we have never been able to discover their 

 branched " pseudopodia," so called, or the slightest evidence of 

 the crawling movement which they are reputed to exhibit, while 

 we can vouch for the actual fixity of some. The soft contents 

 of the Foraminifer are grosser than those of the Diatom. They 

 each consist of a yellowish amber-tinted, or rich brown, more or 

 less homogeneous or granular pulp, interspersed with fatty 

 globules. The essential differences are yet to be detected by the 

 accurate observer of both. 



The connexion of the Foraminifera with the encrusting 

 Corallines, through the genus Orbiculina, is worthy of further 

 investigation. 



Mr. Huxley^s curious genus Thalassicolla would appear to be 

 referable rather to the Diatomacese than the Foraminifera, but 

 I must defer any observations on this subject to a future period. 



