SCIENCE-GOSSIP. 



73 



first segment of the abdomen is visibly longer." 

 This is an exact description of the female V. 

 austtiaca, to which might perhaps be added that 

 the greater degree of pubescence on the legs 

 applies to the outer side of all the tibiae. These 

 are clothed with long black pubescence, similar 

 to that clothing other parts of the insect, but 

 which is not present on the tibiae of V. rufa. 

 The puncturation on all parts is finer, but 

 more especially observable on the clypeus and 

 the four posterior abdominal segments ventrally. 

 The apical ventral segment or plate is more 

 parallel-sided, and is somewhat contracted or 

 shouldered before the emarginate apex. The 

 mandibles are smaller and less rugged, the clypeus 

 is smaller, and of less width across the apex ; and 

 the ligula or tongue is very distinctly smaller than 

 than in V. rufa. The abdomen is more spindle- 

 shaped, due in part to the greater length and the 

 contraction anteriorly of the first abdominal seg- 

 ment. Then there is the greater comparitive width 

 of the second segment, and the first abdominal 

 segment is less abruptly truncate at the base than 

 in V. rufa. The scape of the antennae is yellow in 

 front, and the three black dots on the middle of 

 the clypeus are arranged in a triangle. Length 

 is o 70 inch. 



In the male austtiaca the scape of the antennae 

 is also yellow in front ; but the clypeus is 

 immaculate, and its lower angles, though still den- 

 tate, are less produced. The pubescence on the 

 outer side of the tibiae is sparser, and the black 

 spot on the middle of the first abdominal segment, 

 instead of being button-shaped, as in the female, is 

 lozenge-shaped. All other points of difference 

 enumerated as existing between the female Vespa 

 austtiaca and V. rufa exist also between their 

 respective males ; except in the form of the apical 

 ventral plate of the abdomen and the puncturation 

 of the abdomen ventrally, which is absent in the male 

 austtiaca, and is of varying intensity in the male 

 rufa, though never so abundant or so coarse as in the 

 female form of that species. Length is 0-50 inch. 



The genital armature pretty closely resembles 

 that of the male V. rufa, but is not identical with 

 it ; the entire organ is narrower and much more 

 parallel-sided. The stipites are more closely 

 approximated in the median line dorsally, whilst 

 the semi-membranous ear-like appendage at their 

 apex is larger and stands outwards at a greater 

 angle. The scoop-like united sagittae closely 

 resembles the same part in the V. rufa — is parallel- 

 sided, rounded at apex, and with the convex side 

 Upwards or dorsally set ; whereas in V. vulgaris and 

 V. germannica the united sagittae form a ladle-like 

 instrument, the head or cup of which has the 

 convex side downwards or ventrally set. 



Killittgworth, Newcastle-on-Tyne. 



July, 1898. 



PISIDIUM NITIDUM 



var. LATERALIS. 



By C. S. Coles. 



T N April last I took from a small weedy pond 

 near here a number of a Pisidium which I 

 considered to be P. niiidum ; but not being satisfied 

 as to their identity, I submitted examples to Mr. 

 L. E. Adams, of Stafford, for his opinion of them. 

 That gentleman has informed me that they are 

 really nitidum, but not of the typical form, differing 

 therefrom in not being sufficiently round at the 

 lower margin, and the umbones not central enough. 

 That opinion has been confirmed by Mr. Taylor,' 

 of Leeds, who has also examined the specimens. 



I have since visited the pond, and found the 

 shells tolerably abundant, some of them of large 

 size, but all preserving the above characteristics. 

 The typical form was not obtained. 



I propose for the above variety of P. niiidum the 

 name of lateraiis. 



I observed that the finest specimens inhabited a 

 small grassy cutting at the margin of the pond, 

 where the water scarcely covered the bottom, in 

 which the scoop could only be worked with diffi- 

 culty, and amongst my captives were a fair 

 sprinkling of P. roseum, many of them being also 

 of large size, and these frequented the same 

 cutting as the former species. 



The only other mollusca inhabiting the pond, as 

 far as I have investigated it, are Planorbis complanatus 

 (common) and Sphaerium lacustris, together with a 

 solitary specimen of Helix hispida, which put in an 

 appearance amongst the weeds, etc., dragged from 

 near the centre of the pond. That may, however, 

 easily have travelled to where it was found, from 

 the margin, along the weedy surface, and thence 

 into my scoop. 



Hoe Moor House, Hambledon, Hants. 

 June, 1898. 



Collecting with Surface Net. — Prof. C. A. 

 Kofoid, says "Science," has recently been dis- 

 cussing the Hensen method of collecting. This 

 method of sweeping the plankton consists essentially 

 in drawing a silk net vertically through the water. 

 Its accuracy depends upon the efficiency of the 

 silk in really catching the organisms. Experiments 

 at the Illinois Biological Station show, however, 

 that the leakage is great. The method is satis- 

 factory only for the larger forms, such as the 

 Entomostraca and the larger Rotifera and Protozoa. 

 For the smaller and oiten very abundant " plank- 

 tonts," such as Melosira, Pcridinium, Dinobrvon, 

 Raphidium, Sccnedcsmus, Euglena, Tiachelomona and 

 Chlamydomonas, the Hensen method is wholly 

 inadequate. Of 767,556,000 planktonts retained by 

 the Berkefeld filter per cubic metre, only 248,200 

 organisms per cubic metre were retained in the 

 silk net. This loss by leakage, says Prof. Kofoid, is 

 of prime importance, for it is composed very 

 largely of minute algae, which constitute a 

 fundamental link in aquatic life. — /. H. Cooke. 



