WITH THE MICROSCOPE. I/I 



may be seen to occur slowly in the germinal matter of the cornea 

 of the frog and other animals. Soon after death a shrinking or 

 collapse of the soft germinal matter of all cells takes place, and 

 this alteration has led to the view that the nuclei lie embedded in 

 spaces or vacuoles in the tissues. During life, and especially in the 

 early and more active period of growth, the germinal or living 

 matter is continuous with the tissue, and the shrinking and alteration 

 in question are due to changes which immediately follow the death 

 of this living matter. 



The germinal matter entering into the formation of ova is the 

 seat of active vital movements which may be studied without diffi- 

 culty. In the ova of the common water snail (limnagus stagnalis) 

 complete -rotation occurs, and the embryo from an early period is 

 covered with cilia. Changes in form may be observed in the ova of 

 amphibious reptiles, particularly the frog and newt. Those of tlie 

 pike, stickleback, and many osseous fishes are particularly favourable 

 for observation (Ra-nsom). The stickleback can be easily kept by 

 the microscopist in an aquarium. They sometimes breed in con- 

 finement, and the sort of nest which is made for the protection of 

 the young and guarded by the male, is an object of great interest. 



The movements in germinal matter of the higher animals (mucus, 

 pus) can be distinctly seen with a twelfth of an inch object-glass, but 

 it is oft^n necessary to examine one particular corpuscle very 

 attentively for half a minute or more. In some cases the changes 

 in form are so slow that the observer who looks at the object for 

 the first time cannot satisfy himself of the actual occurrence of the 

 movement at all. It is absolutely useless to attempt observations of 

 this kind in an off-hand, slap-dash, self-asserting manner. Those 

 who desire to have the delight of pondering over such changes will 

 gladly find the leisure to observe the facts. This is just one of 

 those phenomena which, having been well seen once can generally 

 be detected afterwards without much difficulty. Under the sixteenth, 

 twenty-fifth, or fiftieth, the alteration in form can be seen very dis- 

 tinctly, and there are few things more- wonderful, or which will 

 furnish more interesting matter for careful thought and for valuable 

 and useful speculation. 



The movements I have described as vital movements I regard as 

 frimary, and think that the power of movement exists in connection 

 with the matter of which each small portion of the moving mass is 

 composed. It may be to 'some minds unsatisfactory to attribute the 

 phenomenon to the influence of a power of the nature of which 

 nothing is known, but it is surely better to do this for the present, 

 than to assert that these movements are due to physical force, when 



