20 NATURAL HISTORY 



place in some genera symmetrically, as in the Gonia, 

 &c. 3 in others, by transverse, longitudinal, or diagonal 

 sections. In these latter cases the produce have forms 

 differently proportioned from those of the creatures from 

 which they spring ; for instance, figure 160 represents 

 the young of 159, engendered by a transverse division : 

 this circumstance, we may observe, renders it some- 

 times difficult to determine the species. 2. They pro- 

 pagate, in the manner before mentioned of the Volvox, 

 and some other genera, by a distribution of the internal 

 substance of the parent into a proportionate number of 

 young ones, all of which at their birth issue forth, and 

 leave behind them nothing but the envelope, soon to be 

 dissolved. 3. They are produced from germs, shooting 

 forth from the parent's sides, as represented by fig. 218, 

 &c. 4. From spawn, which, in the act of being shed, 

 carries along with it a portion of the parent animalcule, 

 as shewn by figure 80. 



With respect to the mode of viewing animalcules under 

 the Microscope ; I would direct that they be placed in 

 what are termed aquatic live-boxes (described in the 

 '^ Microscopic Cabinet"), or on a slip of glass, in which 

 case they should be covered with a thin plate of mica, 

 which will have the effect of preventing the small quan- 

 tity of water put with them from evaporating, and of 

 rendering the surface perfectly plane for the purpose of 

 observation : an additional advantage, however, will be 

 obtained by making use of my Aplanatic Engiscope, (or 



