412 THE FORMS OF CELLS [ch. 



does not introduce the element of time, and of succession, or discuss 

 their origin and affihation as an historical sequence of events. But 

 in biology, the term species carries with it many large though often 

 vague assumptions; though the doctrine or concept of the "per- 

 manence of species" is dead and gone, yet a certain quasi-permanency 

 is still connoted by the term. If a tiny foraminiferal shell, a Lagena 

 for instance, be found hving to-day, and a shell indistinguishable 

 from it to the eye be found fossil in the Chalk or some still more 

 remote geological formation, the assumption is deemed legitimate 

 that that species has "survived," and has handed down its minute 

 specific character or characters from generation to generation, 

 unchanged for untold milHons of years*. If the ancient forms be 

 Hke to rather than identical with the recent, we still assume an 

 unbroken descent, accompanied by the hereditary transmission of 

 common characters and progressive variations. And if two identical 

 forms be discovered at the ends of the earth, still (with occasional 

 slight reservations on the score of possible "homoplasy") we build 

 hypotheses on this fact of identity, taking it for granted that the 

 two appertain to a common stock, whose dispersal in space must 

 somehow be accounted for, its route traced, its epoch determined, 

 and its causes discussed or discovered. In short, the naturaUst 

 admits no exception to the rule that a natural classification can only 

 be a genealogical one, nor ever doubts that '"The fact that we are able 

 to classify organisms at all in accordance with the structural charac- 

 teristics which they present is due to the fact of their being related by 

 descenf\'' But this great and valuable and even fundamental 

 generahsation sometimes carries us too far. It may be safe and 

 sure and helpful and illuminating when we apply it to such complex 

 entities — such thousand-fold resultants of the combination and 

 permutation of many variable characters — as a horse, a lion or an 

 eagle; but (to my mind) it has, a very different look, and a far less 

 firm foundation, when we attempt to extend it to minute organisms 

 whose specific characters are few and simple, whose simplicity 



* Cf. Bergson, Creative Evolution, p. 107: "Certain Foraminifera have not 

 varied since the Silurian epoch. Unmoved witnesses of the innumerable revolu- 

 tions that have upheaved our planet, the Lingulae are today what they were at 

 the remotest times of the palaeozoic era." 



t Ray Lankester, A.M.N.H. (4), xi, p. 321, 1873. 



