i 7 8 



HA RD WICKE'S S CIENCE- G OSSIP. 



beauty of that romantic spot. Two of the commonest 

 Hong-Kong ferns belong to the real shield-ferns, 

 A. molle, Sw., and A. ttnitum, Sw. Both are alike, 

 and apparently resemble the English male fern, A. 

 /llix-mas, but if the student examine them closely he 

 will find a connection in the veins at the sinus, or 

 bend of each little division, or lobe. Of the veinlets 

 that branch regularly up each segment, a pair meet 

 and terminate at every bend or cut. This meeting of 

 veinlets constitutes the main difference between two 

 of the largest subdivisions of this enormous genus, 

 viz. Lastrea and Nephrodium. A. molle, Sw., and 

 A. unitum, Sw., are both about two feet high, and 

 grow everywhere in the hills and in the town. A. molle 

 is a light green, soft and downy ; A. unitum is darker 

 and more shiny, the former has very few very small 

 sori, often found only close to the rachis. In A. 

 unitum the fructification is dark-coloured, densely- 

 crowded, and closer to the margin of the lobes. 



Gen. XI. Meniscium, Schreb. 



M. simplex, Hk., is not uncommon at the Peak, 

 and is easily distinguished by the very marked raised 

 veins, laid as it were like net-work all over the under 

 side of the frond, which is about 4 or 5 inches long, 

 entire, and very finely pointed, having two half-lobes at 

 the base more or less detached from the main-stem. 

 The long delicate apex is often half the length of the 

 entire leaf. The fertile portion differs materially in 

 being much longer, much narrower, and more up- 

 right than the sterile, and closely packed with the fruc- 

 tification, which is brown and destitute of covering. 



Gen. XII. Polypodium, Linn. 



Every polypody does not resemble our old friend in 

 England, whose yellow buttons of sori and favourite 

 haunts on old trees and ruined walls render it familiar 

 to us all. The technical distinction is the absence of 

 indusium (often overlooked in aspidium, when the 

 indusium is sometimes obsolete or lost). 



There is no polypody common to this neighbourhood. 

 The searcher in the hills might perhaps be rewarded 

 by finding P. adnascens, Sw. — a little fern covered 

 with furry down on the under side, and round sori, 

 or P. lingua, Sw., rather larger, with less down or 

 tomentum and sori at further intervals. In both 

 ferns the frond is entire. 



(To be continued.') 



An Excavation carried on by the German Govern- 

 ment is said, in the Times, to have been in process 

 near Schladebach, with the object of obtaining 

 further information as to the increase of underground 

 temperature. At 1392 metres, the depth reached at 

 the beginning of this year, and believed to be the 

 lowest yet attained by boring, the temperature was 

 49° C. 



THE VARIATION AND ABNORMAL 

 DEVELOPMENT OF THE MOLLUSCA. 



Part II. 



T IMNMA GLUTINOSA. This remarkable 

 / s species belongs, not to Limnrea proper, but 

 the genus Amphipeplea of Nilsson, and is easily 

 known from Limnaea by the fact, that when alive 

 the mantle covers the shell, and in this way and 

 in the texture of the shell it is related to Physa 

 fontinalis. This species is rare and local, and does 

 not vary so much as some of the allied species. 

 In the district we are now dealing with, it has been 

 recorded as living on Barnes Common ; my brother 

 has specimens from Deal, Minster, and Sitting- 

 bourne, and I have found it abundant but local in 

 the St. Nicholas Marshes, where it is easily seen on 

 the leaves of Nuphar luteum and other plants. 

 These St. Nicholas Marsh specimens are rather light 

 in colour, and it was there I found a most curious 

 and interesting monstrosity or variety, which has 

 much the relation to the type of glutinosa that Z. 

 involuta has to Z. peregra. 



This specimen has the spire very short, and sunken, 

 but slightly raised at the apex ; the body whorl is 

 swollen above, and the top of the shell appears nearly 

 flat. Should this form turn up in any other localities 

 it might be called monst. intortum, but as long as we 

 have only a single specimen I think it is better 

 unnamed. 



Limncea peregra. This is the commonest and most 

 variable of our freshwater mollusca. 



I have taken a very globose form, probably var^ 

 ovata, in the Regent's Canal, where the water is 

 stagnant and there is very little weed. (I record the 

 kind of situation when possible, as one often finds 

 that facts, seemingly of no account, are afterwards 

 valuable in drawing conclusions as to the origin and 

 use of variations.) 



A specimen from Chislehurst is slightly decollated, 

 specimens from Bromley and Eltham are somewhat 

 thinner than usual, but my thinnest specimen was 

 taken by my brother at St. Nicholas Marsh. I have 

 an exceeding thick and apparently semi-fossil shell 

 from Barnes, and from what has been said above 

 concerning the Barnes shell it seems improbable that 

 it could have recently lived on the spot. This species 

 occurs fossil at Crayford, but the specimens do not 

 differ from those now living. I have a succinea- 

 shaped specimen taken in a well at Farnborough, 

 it is possibly the variety succinaformis of Jeffreys. 

 A monstrosity from Kew Gardens has a wide and 

 deep umbilicus. A shell I found in a ditch close to 

 \V aimer Castle has a rather long spire with a fairly 

 deep suture, and has a number of confluent whitish 

 bands all of which are below the periphery. (It is 

 remarkable that whenever bands are abnormally 

 developed in the genera Limnaea and Physa, they are 



