ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 473 



We have here a very remarkable example of anatomical and func- 

 tional retrogression. The organs having been reduced, the functions 

 have been concentrated. The diiferentiation of the suctorial and pre- 

 hensile tentacles having ceased, or being absent, the two correlative 

 functions have been compelled to combine in the sam.e organ, which, 

 in its turn, in order the better to perform its now multiple part, has 

 been obliged to modify and adapt itself. We have evidence that this 

 must have taken place when we find that whilst in the other Acinetce 

 the tentacles are usually rigid and motionless, in the present case 

 they are flexible and movable in all directions. 



Foraminiferous Silt Banks of the Isle of Ely. — Mr. James 

 Green, of March, describes these banks as follows : — 



In various parts of the fens of Cambridgeshire, but more particu- 

 larly in the district known as the Isle of Ely, may be found consider- 

 able beds of silt, which give a slightly undulating surface to what 

 would otherwise appear as a perfectly level plane. These banks are 

 generally covered with from one to two feet of the ordinary black 

 vegetable mould, for which these fens are particularly famous. Occa- 

 sionally the silt crops out, and where this is the case it almost assumes 

 the same colour as the surrounding earth. The height of the banks 

 rarely exceeds four or five feet. In the town of March there is a fine 

 sample of one of these silt banks, which has been opened, and large 

 quantities of the silt taken away by brickmakers, to prevent the 

 newly made bricks from adhering one to another before being dried 

 and burned. They have left a large semicircular section of the silt 

 upstanding, somewhat like a wall some four or five feet in height. 

 The beds rest, in most cases, on blue clay, which extends downwards, 

 as far as any local borings have ever been made, some fifty or sixty 

 feet. On carefully examining the section, one may trace thin sinuous 

 lines of a black or greyish tint, running in a nearly horizontal direc- 

 tion, resembling the ripples left on the sand at the sea-shore. The 

 lines were apparently formed in some such manner, as on examining 

 them with a powerful hand-lens large numbers of Foraminifera are 

 seen, which are, in fact, almost exclusively confined to the sinuous 

 lines, the bulk of the silt itself (which is of the colour of yellow 

 ochre) containing none. These greyish lines consist for the most 

 part of shells, fine sand, black specks of what seem to be lignite, and 

 other decayed matter, such as one would expect and would find in the 

 ripples by the shore. 



Mr. Green adds that if any difficulty is found in getting heavy 

 shells to swim by the floating process, strong brine will often accom- 

 plish what the fresh water fails to do. 



Production of Amoebae.* — Professor Nunn gives an account of a 

 discovery she has made of the generation of Amcehce in a remarkable 

 manner from an infusion of the yolk of a hen's egg in Pasteur's fluid. 

 In about ten days, and when the odour of decomposition had begun to 

 be strong, Amcehce were found in such abundance as to form a creamy 

 deposit on the surface of the liquid, and a drop examined from any 



* Amer. Jourti. Micr., vi. (1881) p. 24. 



