144 Proceedings of the Royal Physical Society. 
the latter will also be altered. As, further, the organs of the 
reproductive cells are modified, it stands to reason that the 
embryo derived from them must be modified. 
Theoretically, acquired characters can therefore be trans- 
mitted. I need hardly say I would not acknowledge the 
loss of a tail, eg., in the dog, to be a character capable of 
influencing the offspring of that dog, for the very simple 
reason that the tail has nothing to do with the elaboration of 
food-materials. 
THE MAIN FACTORS IN SEXUAL REPRODUCTION would appear 
to me to be shortly these :— . 
1. The sex cells being parasitic do not undergo any 
special development, and are accustomed at the same time 
to definite kinds of food-materials elaborated by the soma of 
the individual. 
2. Fecundation leads to the union of sets of elements 
derived from different parents, the organs rearranging them- 
selves to their greatest mutual advantage. 
3. Thus a vigorous unicellular individual is formed, 
having a number of “cell organs” with a definite chemical 
constitution, and accustomed to is supplied with a definite 
kind of nourishment. 
4, Next, an endeavour to assimilate food-materials in the 
accustomed form and quantity, and as the individuum 
has to assimilate its own food, having lost its parasitic 
nature, a development of special functions, which latter 
during ontogeny will be successively distributed over 
“cell organs,” cells, and ultimately groups of cells (vde 
above, pp. 139, 140). 
5. But not all the cells derived from the zygote or 
fertilised ovum will undergo a special development for ~ 
mutually benefiting one another, and these will commence 
as soon as possible to revert to or maintain their parasitic 
nature, and develop again into reproductive cells. 
_ VARIABILITY. 
That the offspring differs more or less from its parents is 
an everyday observation, and to our eyes the variability of 
