ORIGIN OF SPECIES. 281 



then the species of an existing family wonld have had at their 

 commencement a parent species from which they proceeded. 

 In this way, Darwin arrives at the first beginnings of things, 

 and assumes that there were only a few primitive fundamental 

 types, from which all the species now living have been developed 

 during an immeasurably long period of time. 



To carry out this hypothesis consistently, we should have to 

 admit that all species had a common origin, and that, becoming 

 modified in the course of ages, they were developed in all direc- 

 tions. They would melt imperceptibly one into the other, so that 

 if we could look over all that had ever been produced, no limit 

 between one species and the species which follows would any- 

 where be found. "What we call a species would be only the 

 form manifested at a certain time, which can be distinguished 

 from the allied species only because all intermediate forms have 

 been lost, and have remained unknown to us j and if we could 

 discover these intermediate forms which once existed, all dis- 

 tinction of species would disappear. But everywhere in nature 

 we see well-defined species, so that Darwin had to assume that 

 we know only a very small portion of the plants and animals 

 that have existed, and as it would be very remarkable if, in so 

 extremely incomplete a series, any harmonious gradation had 

 been displayed, the adherents of Darwin as much as possible 

 explain away this gradation or deny it altogether. 



A.S the Darwinian hypothesis seems to solve the great enigma 

 of the origin and extinction of species in the simplest manner, 

 Prof. Heer now inquires whether the natural phenomena of 

 Switzerland admit of such an interpretation. 



It has been observed that certain species pass from one geo- 

 logical period into the following one, and that of the Swiss 

 Miocene marine Mollusca, even thirty-five per cent, are still 

 in existence (pp. 91, 92). The descent of living individuals 

 from those of the Tertiary period cannot be regarded as doubt- 

 ful. Other species certainly differ in more or less essential 

 points from those of the preceding period, but yet approach them 

 so closely that we must assume the ancient species to have co- 

 operated in their production ; and we cannot well imagine this 

 cooperation to have taken place otherwise than by descent from 

 the older species, the existing differences having been produced 



