464 
Transactions of the Society. 
A persistent species-maker was tlie late Mr. Eattray, who, in his 
monogra'phs of several of the disciform genera, admits many forms as 
species which appear to me to graduate into each other, or to be 
distinguished by such trifling variations as sometimes occur in the 
valves of the same frustule. From Schmidt’s figures he names 23 
as specifically distinct, although the original observer, who had the 
opportunity of examining the specimens, did not so regard them. 
With reference to the excessive multiplication of species, the fol- 
lowing remarks of Mr. H. C. Watson are appropriate, although origi- 
nally penned with reference to higher plants. “ The 4 splitters ’ will 
too often * make a species,’ resting on difference of a very slight kind 
or degree, if they expect or hope to find them constant — rather that 
nobody will find them inconstant. Usually, all they look for is 
some difference which can be expressed in technical language or 
shown in portrait drawings, while they leave to others the far less 
facile task of trying whether the difference is constant or inconstant, 
of proving that the characters of the two alleged species are con- 
vertible, if such be the case. . . . However injudicious or precipitate 
he may be, the species-maker has thus the chances largely in his 
favour for maintaining the species, truly or falsely so-called.” 
In the most recently published important treatises on diatoms, 
there is an evident reaction against such extreme “ splitting.” Dr. 
Yan Heurck, in his ‘ Synopsis des Diatomes de Belgique,’ * expressed 
his views thus : <c If it be difficult, when treating of the higher 
plants, to define the relative value of forms, it is still more so when 
treating of very minute diatoms, and it is almost impossible, with 
our present knowledge at any rate, to fix with certainty the limits 
of species, or even to admit the existence of them. Practically the 
forms are so closely connected, that in many cases intermediate forms 
may be referred indifferently to two different types. It is by study- 
ing attentively numerous diatoms that we can see that these organ- 
isms form a continuous chain, which we break up artificially to form 
links, the number and importance of which vary according to indi- 
vidual opinion.” This was in 1880; sixteen years afterwards, he 
writes, “ With reference to species my ideas have not undergone any 
alteration.” He refers to “ primordial species,” and adds, “ It may 
be assumed that our many existing forms sprang from one or from 
several primitive forms. These primordial forms have given birth to 
secondary, tertiary forms, &c., which were differentiated in certain 
directions, and which have continued to evolve more or less in those 
directions.”! And again: “It is therefore more logical to admit 
that the apparent transitions recorded arise from the fact that authors 
have created different ‘ species ’ at the expense of varieties or of races 
of the same specific type-form, and that true species are in reality 
much less numerous than has hitherto been imagined. It cannot 
happen, therefore, till research has been much further prolonged, that 
* P. 41. t P- 99- 
