78 THE MICROSCOPE AND ITS REVELATIONS. 



down to depths of from 1,000 to 2,500 fathoms, have brought up few 

 forms of either l porcellanous ' or i vitreous ' Foraminifera that were not 

 previously known, they have added greatly to our knowledge of the 

 'arenaceous' types, the number and variety of which far exceed all 

 previous conception. These have not yet been systematically described; 

 but the following notice of a few of the more remarkable, will give some 

 idea of the interest attaching to this portion of the new Fauna which has 

 been brought to light by Deep-sea exploration. 



473. In the midst of the sandy mud which formed the bottom where 

 the warm area of the ' Globigerina-mud ' ( 480) abutted on that over 

 which a glacial stream flowed, there were found a number of little pellets, 

 varying in size from a large pin's head to that of a large pea, formed of 

 an aggregation of sand-grains, minute Foraminifers, etc., held together 

 by a tenacious protoplasmic substance. On tearing these open, the whole 

 interior was found to have the same composition; and no trace of any 

 structural arrangement could be discovered in their mass. Hence they 

 might be supposed to be mere accidental agglomerations, were it not for 

 their conformity to the 'monerozoic' type previously described ( 393); 

 for just as a simple ' moner,' by a differentiation of its homogeneous sar- 

 code, becomes an Amceba, so would one of these uniform blendings of 

 sand and sarcode, by a separation of its two components, the sand form- 

 ing the investing ' test,' and the sarcode occupying its interior, become 

 the arenaceous Astrorliiza. This type, which abounds on the sea-bed in 

 certain localities, presents remarkable variations of form : being sometimes 

 globular, sometimes stellate, sometimes cervicorn. But the same general 

 arrangement prevails throughout; the cavity being occupied by a dark-- 

 green sarcode, whilst the 'test' is composed of loosely aggregated sand- 

 grains not held together by any recognizable cement, and has no definite 

 orifice, so that the pseudopodia must issue from interstices between the 

 sand-grains, which spaces are probably occupied during life with living 

 protoplasm, that continues to hold together the sand-grains after death. 

 These are by no means microscopic forms; the ' stellate ' varieties ranging 

 to 0.3 or even 0.4 inch in diameter, and the ' cervicorn ' to nearly 0.5 

 inch in length. 1 



474. The purely Arenaceous Foraminifera are arranged by Mr. H. B. 

 Brady 3 (by whom they have been specially studied) under two Families: 

 the first of which, Astrorliizida, includes with the preceding a number 

 of coarse sandy forms, usually of considerable size, and essentially 

 monothalamous, though sometimes imperfectly chambered by constric- 

 tions at intervals. Some of the more interesting examples of this family 

 will now be noticed; beginning with the Saccamina (Sars), which is a 

 remarkably regular type, composed of coarse sand-grains firmly cemented 

 together in a globular form, so as to form a wall nearly smooth on the 

 outer, though rough on the inner surface, with a projecting neck sur- 

 rounding a circular mouth (Fig. 319,* a, b, c 9 ). This type, which occurs 

 in extraordinary abundance in certain localities (as the entrance of the 

 Christiania-f jord), is of peculiar interest from the fact that it has been 

 discovered in a fossil state by Mr. H. B. Brady, in a clay seam between 

 two layers of Carboniferous Limestone. Its size is that of very minute 

 seeds. In striking contrast to the preceding is another single-chambered 



1 See the description and figures of this type given by the Author in "Quart. 

 Journ. Microsc. Sci.," Vol. xvi (1876), p. 221. 



2 See his " Notes " in " Quart Journ. of Microsc. Soc.,"N.S., Vol. xix. (1879), p. 

 20 ; and Vol. xxi. (1881), p. 31. 



