Anctbolism and Specialisation. 207 



would attain to a greater size, as it would require less surface 

 in relation to its bulk. The greater excretion of waste 

 products in the first case would also tend to the cell having 

 a greater surface in comparison with its bulk. Contractile 

 vacuoles and the presence of cilia would allow of the attain- 

 ment of greater size, but the use of these would involve the 

 expenditure of greater energy, with a necessity of greater 

 nutrition. Forms of life with many cilia appear to be able 

 to attain to a greater limit of growth than those which have 

 but one cilium or flagellum. The more sluggish amoeboid 

 forms attain a larger size, and are probably aided in this by 

 their contractile vacuoles and constant change of surface. 

 These are surpassed by still more passive forms, which have 

 acquired a high degree of nutrition through the parasitic 

 habit. The size acquired by cells would seem to depend not 

 only on the amount of nutrition available, and the relation 

 between the surface and the cubic contents of the cell, but 

 also upon whether the form of anabolism was to the produc- 

 tion of a more stable or a more unstable form of protoplasm. 

 The cells of degenerate forms of plants, like the Fungi, whose 

 form of anabolism is of a less stable type, appear to favour 

 either small size or a large superficies in relation to their 

 bulk, which latter is well seen in the mycelial habit. The 

 largest cells in animals are ova; these are often packed with 

 the products of a less elaborate form of anabolism, and, in fact, 

 to such an extent is this process sometimes carried, that parts 

 of the ovaries pass over into the condition of vitellaria, where 

 the cells consist of these unelaborated products. 



In comparing the two types of germ cell, the ova and the 

 sperms, which hold good in contrasting these two forms of 

 anabolism in a more or less marked degree, the tendency of 

 the ovum is to a greater size, a spherical shape, less elabora- 

 tion and more stability in the products of anabolism, and a 

 reluctance to division. The sperm, on the other hand, shows 

 the instability of the products of its anabolism in its small 

 size, the comparatively large extent of its surface, and a 

 tendency to division until its powers of anabolism can only 

 keep pace with its constant loss of energy. This great 

 tendency to division in the early stages of formation 



