312 Miscellaneous, 



show clearly that it ia a new form of the most remarkable kind as 

 regards its characters, its development, and its zoological affinities. 



In the normal adult state it appears in the form of isolated, ovoid, 

 elongated shells, from 1 to 2 millim. in length, monaxial and per- 

 forated by a mouth at one of their poles. The study of this enve- 

 lope elucidates the question, hitherto so obscure, of the development 

 of the test in the Rhizopoda. In the young state it is thin, purely 

 chitinous, with an alveolar structure, which is often very distinct. 

 It thickens by the division of its areolse into two and then into 

 several layers ; the two peripheral layers, internal and external, 

 persist in the chitinous state, while the intermediate areolae become 

 charged with calcareous matter, which thus forms a series of glo- 

 bules, often arranged in regular rows. The internal layer is the 

 primary fundamental membrane of authors. The preceding state- 

 ments demonstrate the falsity of the theory of the growth of the test 

 of Rbizopoda by apposition, as well as several other hypotheses cha- 

 racterizing the present state of science ; growth takes place through- 

 out the thickness of the test, as if the whole envelope were living. 

 The protoplasmic body contained in the shell, which presents all 

 sorts of tints, from brownish yellow to bright rose-colour, is sur- 

 rounded by a delicate membrane of cuticular aspect. It presents 

 an areolar structure, which is fine in the peripheral region, with 

 larger meshes in the interior protoplasm. It is far from always 

 filling the whole shell ; often there is only a small dense mass, from 

 which issue anastomosing bands running towards the mouth, where 

 an accumulation of clear substances is formed. There are all pas- 

 sages between these different states and a number of others which 

 it would take too long to enumerate here. 



From the buccal protoplasmic accumulations issue fine trans- 

 parent pseudopodia of variable number, which serve for the prehen- 

 sion of the creatui'es destined to the nourishment of these organisms. 

 In cases where the pseudopodia are all retracted we may see, at the 

 buccal pole, a most remarkable arrangement, unique, at present, in 

 the group of Foraminifera. There is here an excavation of no great 

 regularity, at the bottom of which is the entrance of a tube analo- 

 gous in its aspect to the oesophageal tube of many Infusoria. 



The number and aspect of the nuclei are very variable. Often 

 not very abundant, pale and large, they are in other cases small, 

 refractive, and in larger number. The appearance of these nuclear 

 corpuscles coincides with the commencement of reproduction. 



The reproductive phenomena appear to be produced as follows : — 

 In the peripheral region, around each nucleus, by a sort of gemma- 

 tion, the group of dense protoplasm becomes surrounded by a chiti- 

 nous layer, and in this way are formed a number of small embryos, 

 which, during growth,- divide abundantly, and, after attaining cer- 

 tain dimensions, issue through the mouth. A free young organism 

 is provided with a chitinous shell perforated by a pore and containing 

 a small external nucleus. This embryonic chamber soon produces, 

 by gemmation, a small elongated chamber, which becomes spirally 

 twisted around it ; this first chamber produces a second by the same 



