203 



SCIE'NCE-GOSSIPo 



[Sept. 1, 1865. 



green contents are arranged round double nuclei, on 

 each side of the constriction ; and at times (probably 

 before the increase by cell-division takes place) dark- 

 coloured particles, having a peculiar " swarming " 

 motion, may be seen between each pair of nuclei. 

 Perhaps in no plant can the processes of cell-division 

 and conjugation be more readily traced. 



rigs. 1 to 4 show the mode in which cell-division 

 takes place. The constriction across the frustule 



qecomes wider, and a small protuberance appears 

 between the two half cells, across which a wall 

 of separation seems already to have been formed. 

 The parts of this protuberance gradually enlarge, at 

 first containing only the " swarming " particles ; then 

 assuming the form and colour of the corresponding 

 half cells ; and at length, when tlie growth is com- 

 plete, separating into two perfect frustules. In these 

 the process of cell-division is again repeated, so that 

 the multiphcation of these simple plants under 

 favourable circumstances must be exceedingly rapid ; 

 though there is, doubtless, a limit beyond which the 

 multiplication does not extend. 



In conjugation two cells, which are near to one 

 another, each divide at the constriction, and pour 



out their contents into one common mass (fig. 6) 

 which is held together by a gelatinous envelope. 

 This mass, which at first is of irregular shape (figs. 

 6, 7), and contains small transparent, colourless 

 globules (possibly of oil), gradually obtains a more 

 regular form (fig. 8), and at length becomes a spheri- 

 cal sporange, convered with forked protuberances 

 (fig. 10*). 



The contents of the sporange at first seem to con- 

 sist of irregular, rounded green masses. Afterwards 

 these become either uniformly blended, or else in- 

 crease so as to fill up the sporange, which then pre- 

 sents a dark green aspect. Subsequently the con- 

 tents appear as a central, green mass, surrounded 

 with purplish matter; and, being to some extent, 

 less in bulk, make the surrounding cell-wall very 

 apparent. 



That the sporanges, after a time, break up and pro- 

 duce new plants is very evident ; though it is diffi- 

 cult to detect when or how this takes place. A mass 

 of cells (fig. 12) may, perhaps, be an early stage in 

 their development; for such masses occur abund- 

 antly in the water in which the Cosmarium is kept, 

 and bear a considerable likeness to the perfect 

 frustules. J. S. Ttjte. 



THE COMMON DORMOUSE 



{Myoxus avellanarius.) 



I THINK I am right when I say that very few 

 persons know the great iaterest this little ani- 

 mal is capable of affording, except, of course, those 

 who have cultivated its acquaintance by keeping it 

 as a pet,— interest not only as regards its habits and 

 mode of life during both summer and winter, but 

 also as to the variety of food it requires, and the 

 enormous quantity of that food which, for so small 

 a creature, it will consume ; together with the amuse- 

 ment produced by watching its innocent gambols 

 during its hours of feeding. 



The Dormouse is indeed, as described by MUne- 

 Edwards, in his work on Natural History, a pretty 

 little animal, with soft hair, velvety tail, ever tufted, 

 with a lively look, having a strong analogy to the 

 rat ; it belongs to a genus of the Linnfean order 

 GHres, and it inhabits temperate and warm countiies, 

 subsisting entirely on vegetable food. In Varro, De 

 Be Riistica., we find that the art of rearing and fat- 

 tening great numbers of this genus was practised in 

 lioman villas, as a profitable article of rural economy; 

 and again in Brotier, the last edition of Pliny, we 

 read that the excessive demand of them for luxurious 

 tables was increased by the foolish prohibitions of 

 the censors ; and it is reported that they are still 

 esteemed in modern Rome, being frequently sent as 



* Fig. 10— a is the earlier, h the more perfect form of these 

 protuberances, 



