On tlic Development of Paliulitia vivipara. 291 



taneously, or in succession. Naturally, it is the stronger plants which 

 most frequently multiply thus, but plants of a smaller number of proto- 

 phylls may branch in this way. One plant of a single protophyll was 

 found with two tubers forming. 



The occasional occurrence of branching in the strobilus might be 

 interpreted as an indication that the ancestors of the plant were once 

 more abundantly branched. But it would be possible to take the 

 opposite view that such branching is a nascent feature, that it is a new 

 feature in the phylogeny. Bertrand regarded Phylloglossum as a form 

 reduced on account of its semi-aquatic mode of life. But it is 

 necessary to point out that Phylloglossum is not a setni-aquatic ; 

 Bertrand never had the advantage of seeing the plant in its native 

 home. Phylloglossum, it is true, being a very small plant, can only 

 grow whilst the surface soil is fairly moist, hence it forms a tuber and 

 rests during the dry season. So far as I have seen, the plant grows 

 rather better on a hill-top ; or, at any rate, it grows there at least as 

 well as it does lower down on the slope, and I have never found it in 

 an actual swamp. It grows well on a slope where water can never 

 lodge. Its roots spread rather horizontally, and seldom far downwards 

 in the ground, as though it objected to a waterlogged soil. 



Whilst it is possible that evidence may yet be adduced that Phyllo- 

 glossum in some measure owes its simplicity to reduction, there 

 appears to be little evidence for this at present. On the other 

 hand, it may yet prove that Phylloglossum is an exceedingly primi- 

 tive plant, possibly the most primitive of existing Pteridophytes. 

 We have an explanation ready to hand of this exceptional retention 

 of ancient characters, namely, the annual renewal of the embryonic- 

 stage in the formation of the protocorm. But however this may 

 l>e decided, the relatively simple character of the gametophyte and the 

 comparison of the mature sporophyte with the embryo of Lycopodium 

 cernnniu are in favour of the view that Phylloglossum is the most 

 primitive of existing Lycopodinse. 



" Notes on the Development of Paludina vivipara, with Special 

 Eeference to the Urinogenital Organs and Theories of 

 Gasteropod Torsion. (Preliminary Note.)" By ISABELLA M. 

 DRUMMOND. Communicated by Professor W. F. K. WELDON, 

 F.R.S. Received November 26, Read December 5, 1901. 



I. TJte Urinogenital Organs. 



Von Erlanger, in his work on the development of Paludina, made 

 known for the first time the existence, at an early stage of develop- 

 ment, of a rudimentary kidney belonging to the original left side of 



