638 THE DISEASES AND DISOEDEES OF THE OX. 



line of demarcation can be drawn betwixt animals on tbe one 

 hand and plants on the other. In short, the lowest living things 

 cannot be said to belong either to the one great kingdom or to 

 the other ; but, as we gradually ascend the scale of life, we can 

 discern the successive steps by which the line of division becomes 

 more and more distinctly clear. 



Now, this statement holds with regard to all the processes of 

 life, to the means whereby offspring are produced, no less than in 

 reference to other functions and other features. In the more 

 lowly developed organisms the process of reproduction is a very 

 simple one indeed, consisting as it does merely in the splitting 

 of the parent into two distinct portions, or in the budding off 

 of a small offshoot which gradually grows and grows into the 

 form, shape, and size of the parent. On the other hand, it is 

 remarkable how different is the process of reproduction in higher 

 animals from that which obtains in higher plants. 



In the most lowly developed organisms, as we have j ust said, 

 the process of reproduction is, comparatively speaking, very 

 simple. It may be well, however, to observe here that we have 

 in all probability much yet to learn of the life history of the 

 lowest forms of organisms. It was until recently supposed that 

 reproduction among them was confined to the mere splitting of 

 the parent into two distinct portions, or to the budding off of a 

 small offshoot which gradually acquired the characters of the 

 parent. That this is not the whole matter, is clear as regards 

 the three saprophytic parasites whose life-histories have been 

 80 admirably elaborated by the Rev. Dr. Dallinger. These 

 monads, after giving birth to many generations by the simple 

 process of fission, enter upon an amoeba-stage in which sexual 

 congress is necessary for further multiplication. And we may 

 well hesitate before we subscribe to the belief that sexual 

 congress is not an essential from time to time in the life history 

 of others of the lowly forms of life in which as yet only multi- 

 plication by fission has been observed. Still it is remarkable to 

 note the increasing complexity of the process of reproduction 

 as we ascend the scale of living things. 



Under the ordinary circumstances and conditions of life, each 

 living being gives rise to the production of another being, which 

 gradually becomes more and more like itself ; and if we note by 

 the aid of the microscope how, even in the case of the minutest 



