HARDWICKE'S SCIENCE-GOSSIP. 



part also where the animals cohere has a narrow 

 surface at the point of union. The form of the bivalve 

 cuirass ahvaj's conforms to that of the animal. 



The cuirass of Surirella is not a single piece, but 

 opens in the direction of the length of the animalcule 

 (fig. 8 ). Each valve has the form of a plate, and 

 which fit into each other in a peculiar manner by 

 •means of a species of hinge, very much resembling 

 a round tobacco box. On the margins are a series of 

 elevations and depressions of equal size. In Surirella, 

 JVavicuhi, Closterium and Cosmariuin, the epiderm 

 lines the whole internal surface of the cuirass, forming 

 a sac. 



In 6". Venus the epidermis is manifestly endowed 



Fig. 9. — Friistiilia agrcstis (Corda), two animalcules united. 

 loii, do. do. ^, y, upright and apart; c, d, tlie canals 

 uniting them. 11. View of pedal surface ; c, d, apertures in 

 the same, canals withdrawn. 12. Side view ; g, h, two small 

 openings at the euds (not seen in the figure) ; c, d, openings 

 for the canals. 



o 00 01 



Fig. TO. — Diaioma fenestrafum (Corda). a, colouring matter 

 contained in the cells oi d ; b, side view ; c, intestinal tube 

 common to the series of animals. 



-with muscular power, as we see when the sac opens, it 

 also opens the valves, and when it contracts it closes 

 them. 



Organs of Movement. — Tlie movement of these 

 animalcules is produced by very simple organs where 

 they exist, or by the whole body. 



When describing the cuirass and mantle, I spoke 

 of the feet protruding through the apertures in the 

 •cuirass, and of those formed by the elevation and 

 extension of the mantle. These feet cannot be easily 

 seen ; but in the large species of Xavicula and Frus- 

 tulia, they are distinctly visible. In Pharyngoglossa 

 sigmoidea (fig. 4) above the plug a is a longi- 

 tudinal cleft, through which the foot b is protruded ; 

 a similar foot c is seen at the posterior end of the 

 body, at the termination of the intestinal canal. 



In Frustulia viridescens (fig. 6) these feet are 



plainly discernible. In Scalptriini striatum (fig. 7) 

 we find two openings a, a, near the extremities of the 

 body, and one b in the centre. 



Movement in the animalcules is rarely produced 

 by vesicular feet. The Naviculas and Frustulias swim 

 by a very gentle movement of the whole body. 



The Frustulias move at the rate of a line (j'g of an 

 English inch) in from 1510 20 seconds. This is much 

 faster than Smith states it to be (" .Synopsis," vol. i. 

 p. xxiii). He gives the rate of progress as follows : 



Bacillaria paradoxa 



I 



200' 



Finnularia radiosa 



1 



STOil' 



p. oblonga ,^, Nitzschia linearis 5^, and Pleurosigma 



Fig. ir. — Syrinx anmdatuin (Corda), frustule and valve; 

 a, b, intestinal tube ; c, cuirass; e, annular folds; d, contents. 



strigosuvi nj'fju inch in one second of time. Our river 

 Diatoms scarcely move at all, but those living in the 

 sea are much more lively. 



(Tb be continued.) 



PULEX IRRIT.\NS. — F. Farrant makes some in- 

 quiry about fleas. When I was a boy we were rather 

 interested about fleas, and so put three or four into a 

 glass tube with a little cotton wool at one end ; they 

 fixed their eggs singly to the wool, and we used to feed 

 them by taking the cork out, and putting the open 

 end on the back of the hand, when the fleas would 

 come down to feed. In some parts, where fleas 

 abound, it is not pleasant, but not uncommon to find 

 the grubs in the blankets. From specimens I have 

 mounted for the microscope each flea will lay five 

 eggs at a time. Talking of fleas, I would remark that 

 African ones are darker coloured than English ones. 

 Their apparatus for piercing and sucking is well worth 

 noticing, but requires rather a high power to see 

 with. —Edward Thomas Scott. 



Cormorants. — In this neighbourhood there is a 

 beautiful lake. Lough Owel, and upon a very small 

 and nearly submerged island near Mount Murray, 

 indeed close to the lawn, are a few alder-trees ; upon 

 these we have counted upwards of thirteen cormor- 

 ants at one time, perching upon the stunted trees and 

 giving them a most singular appearance. Lough 

 Owel is about sixty miles from the sea.— /^ /. B. 



