HA RD WICKE' S SCIENCE- G OS SIP. 



127 



which illustrate the species found by me, applies only 

 to figs. 7S and So, c and E. 



Later on, in the course of our cold season I obtained 

 in the same glass bowls and water, numerous speci- 

 mens of "the little-known Hedriocystis pellucida of 

 Hertwig." Four sketches of this rare organism 

 accompany : A (Fig. 72) was drawn under a J-inch 

 Economic objective ; B, C, and D (Figs. 73, 74, 75) 

 under a jg-inch w. i. of Seibert ; D being projected 

 at about double the normal distance in order to get 

 clear details of a well developed, favourably placed 

 specimen. In B (Fig. 73) we have an average He- 

 driocystis, while in C (Fig. 74) there is an abnormally 

 irregular and abundant development of pseudopodial 

 threadlets. The scale which accompanies these 

 sketches applies only to B and c (Figs. 73, 74). Mr. 

 "Wood-Mason has kindly let me have the following 

 note descriptive of this organism : " Stalked shell, 

 round to oval, perforated by numerous holes drawn 

 out into pointed bases ; small (o - 02 to 0*03 mm.) : 

 protoplasmic body only partially fills the shell, with a 

 central nucleus, and several contractile vacuoles in 

 its peripheral parts. Pseudopodia not branched, and 

 not anastomozed. Multiplies by simple fission ; 

 encystment observed. Stalk 0^05 to 0*075 mm - 

 long ; lower end broadened for attachment ; upper 

 passes without sharp boundary into contours of shell." 

 It will be noticed that this description does not quite 

 correspond to my sketches ; e.g. the stalk in my 

 illustrations seems to be cut off by the sharp contour 

 of the lower part of the "shell." This may be 

 explained by my having sketched organisms in which 

 the stalk merged into the " shell " behind the plane 

 under observation. In two specimens killed with 

 osmic acid solution the stalk was distinctly seen to 

 pass without a sharp boundary into the "shell." 

 Then, again, as regards the " shell," I will not say it 

 is, but it looks very like a delicate membrane ; and 

 this leads me to enquire whether or not Hedriocystis 

 may be a stage in the development of Glathrulina ? I 

 am bound to add that I have not been able to detect 

 any silicifying process, or any approach to the forma- 

 tion of the lattice-work, which is so conspicuous a 

 feature in Clathrulina ; but while I frequently meet 

 with the empty carapaces of Clathrulina in the debris 

 at the bottom of my bowls I have not yet found the 

 empty " shells " of Hedriocystis, though I have looked 

 for them. One noteworthy circumstance in connection 

 with the two stalked Actinophryans described above 

 is that they were both obtained after the water had 

 been drawn from the General's Tank for some weeks ; 

 tie loss by evaporation having been meanwhile kept 

 up by occasional additions of pure water, while the 

 supply of oxygen was maintained by the weeds in the 

 bowl : when first drawn neither Clathrulina nor 

 Hedriocystis was detected. So far as I am aware, 

 this is also the first record of the discovery in this 

 country of Hertwig's Hedriocystis. 



Calcutta. W. J. Simmons. 



ON THE SCHEMATISM OF SHELLS IN 

 MOLLUSCA GLOSSOPHORA. 



THE shells of Glossophora exhibit a wide variety 

 of forms, but are as a rule merely variations 

 on the simple spiral. Now, since in these days 

 we are not accustomed to consider variations at 

 mere "freaks of nature," but try to elicit their 

 meaning and bearing on past history (on the hypo- 

 thesis that "nature " is not given to making meaning- 

 less freaks for the fun of it), it seems rather strange 

 that we so seldom hear of any attempt to elicit 

 evolutionary facts from the shapes of the shells which 

 we study. I should like therefore to suggest the 

 following series of hypotheses to the attention of con- 

 chologists. (I.) That the earliest form of shell was 

 probably a bilaterally symmetrical cone. Of this there 

 seems little doubt : but subsequently, as it seems to 

 me, the shell became tapering and cylindrical, and 

 next (II.) became incurved, probably from reasons of 

 mechanical convenience, which it is easy to imagine. 

 Something of this sort is to be observed in certain 

 existing shells (by "reminiscence" probably) and 

 the geologists will be able to give us instances from 

 the Cephalopoda. (HI.) Next comes the flat-coiled 

 spiral, of which, instances from the Cephalopoda of 

 past ages are numerous, and we see the same kind of 

 thing to-day in a typical Planorbis, e.g. P. spirorbis. 

 (IV.) After this stage we find the peristome placed a 

 little sideways (cf. Planorbis comeus), which arrange- 

 ment, as well as the other steps to a certain extent, 

 I think I could demonstrate to be due to reasons of 

 anatomical convenience. Here usually we find the 

 principle of carination most evident, i.e. in the 

 majority of forms : it seems to be due to compression, 

 and to be the same thing in principle as babylonism. 

 (V.) Next we come to the forms in which the spire 

 begins to be more prominent, either, as in our three 

 common Helices, by the enlargement of the last 

 whorl (possibly a sort of reversion), or by depression 

 of the peristome below the preceding whorl, as in 

 Bythinia Leachii or Limnaa tritncatula ; the begin- 

 nings of which process in these cases are suggested by 

 Valvata piscinalis and Planorbis dilatatus * respec- 

 tively. Eventually either the last whorl predominates, 

 as in extreme L. auriadaria, or the spire, as in 

 Turritella and many others. 



Of course this is not intended in any sense as a 

 classification ; indeed, a certain amount of experience 

 has taught me to regard as artificial any too 

 regularly formulated scheme of arrangement. But 

 the above suggestions may be of service to those who 

 are investigating the phylogeny of any group of 

 mollusca. For instance, the valvatiform young of 

 Paludina vivipara would be perfectly intelligible to 

 one who regarded as probable the precedence given to 

 flat uncompressed spirals in the above " fistular 



* But better by some other foreign Planorbes. 



