170 MARINE BIOLOGICAL LABORATORY. 



ference of form, always indicates difference of material 

 substance." This doctrine of " Form and Matter," or 

 of " Mechanism and Function," as expressed in the 

 language of physiology, is the basis of our biological 

 inquiries. As is clearly expressed in the words of Pro- 

 fessor Burdon Sanderson, we must assume that ''every 

 appreciable dijference of s timet lire eorrespoiids to a differ- 

 ence of function ; and conversely, each endowment of 

 a living organ must be explained, if explained at all, 

 as springing from its structure"; or in short, ''living 

 material acts by virtiie of its structure, provided we allow 

 the term structure to be used in a sense which carries 

 it beyond the limits of anatomical investigation, i.e. be- 

 yond the knowledge which can be attained either by the 

 scalpel or the microscope." Given protoplasm of defi- 

 nite structure, and we have its definite function or 

 property. Or conversely, we observe a certain property 

 in a given mass of protoplasm and we regard it as 

 springing from a definite structure. Wlien structure 

 varies, the function must vary also ; and when we ob- 

 serve certain peculiar properties we must ascribe them 

 to peculiarities in structure. 



One rational answer to our first inquiry is possible, 

 viz. the protoplasmic structure of the Q,gg which gives 

 rise to one organism, must differ from that of the ^g^ 

 which gives rise to another different organism, the dif- 

 ferences between the two being relatively as great as 

 those which the two adult organisms display in their 

 anatomical relationships. 



If the similarities of two organisms must be attributed 

 to the corresponding similarities of the protoplasm of 

 the fertilized ova from which they respectively arise, 



