EDITORIAL NOTES. 67 



Following upon Prof. Boycott's discovery of p.irthenogenesis in Paludes/n'na 

 Ji-iikiiisi, Mr. G. C. Ko])son, of the Natural History Museum, has issued the fol- 

 lowing : — 



23/7/19. 



" Dear Mr. 



Mr. J. B. Gatenby, of University College, and I are studying the question 

 of Parthenogenicity in Paludestrina jenkinsi recently made known by Dr. 

 Boycott, F.R.S. 



We are most anxious to obtain the following for our work : — 



1. Paludestrina jenkinsi from brackish or estuarine water. 



2. ,, taylcri from any locality. 



3. , ,, ventrosa from any locality. 



4. ,, stagnalis from brackish and salt water. 



sc. = Hyd7obia iilvcr. 

 I wonder if you have any preserved (spirit) material of these forms 

 from the above localities, or if you are likely to lie going to any place where 

 you might be able to obtain some for us. I would be most grateful for any 

 you could send me ; and would refund any postage for parcels sent. The 

 latter should be marked with a capital P to ensure prompt attention. The 

 animals should be collected alive, and packed in a box with moist weeds and 

 a little mud. If possible they might be sent in a small glass bottle, in the 

 same water as that in which they are found. The bottle can be sent in a 

 wooden box. Precise localities should be given on a label. If you are un- 

 able to do anything for us, would you kindly ask any friend of yours who 

 might be able to do so ? 



Believe me, yours sincerely, 



- G. C. ROBSON." 



NOTE ON THE REPRODUCTION OF OBELISCUS 

 OBELISCUS (Moricand)). 



By GEO. C. SPENCE. 



(Read before the Society, February 12th, 1919). 



On cleaning out tlie shells of two specimens of this fine Brazilian 

 snail I found in one eight embryonic young (largest 8 x 3-5 mm.) 

 and in the other the same number of eggs. These latter measure 

 5 "5 X 4 mm., are a regular oval shape, and have a remarkably thick 

 calcareous shell of old-ivory colour (probably originally whitish but 

 stained by the decayed animal matter) with a smooth half-polished 

 surface. 



Obelisais is described in Tryon's Manual, vol. xviii., page 240, as 

 being viviparous, but this species at any rate appears to be ovo- 

 viviparous. The embryos grow considerably (vide above measure- 

 ments) between the absorption of the calcareous egg-shell and their 

 birth, at which, according to Moricand, they are enclosed in " a cap- 

 sule of clear limpid fluid confined by an extremely thin membrane " 

 — See Tryon's Manual, vol. xviii., plate 34, fig. 48. 



