546 Transactions of the Society. 



Mr. Kousselet suggested that I might supplement this work by 

 a monographic study of the family. Time and circumstances made 

 this impossible, and it was decided to contribute what I could to 

 the knowledge of the group by publishing figures of all the >species 

 I had seen, apart from those illustrated in the two papers above 

 mentioned. These amounted to about a score of species, so that 

 in the three papers, including the present one, fifty species of the 

 family are illustrated and described. Twenty-two of these are 

 species previously undescribed. 



A critical list which I have made of the species in this family, 

 from which I exclude all names which are certainly synonyms and 

 all which are insufficiently described, contains only sixty-seven 

 species, including all my new species. Some half-dozen or more 

 of those in this list are almost certainly unrecognizable, though I 

 have not felt justified in excluding them, as they possess sufficiently 

 distinct characters if we could have confidence in the observations. 



In describing some of the new species, it is quite likely that I 

 have bad under observation animals previously described, but if 

 so, described in such a manner that it is impossible to detect the 

 identity. 



Some species have been described without accompanying 

 figures. All of these I reject without hesitation, as I consider it 

 quite impossible to make a description of a species which shall 

 serve for certain identification without the assistance of a figure. 

 Tlie figure is the important thing ; the written description merely 

 an explanation of the figure, calling attention to characters which 

 might be overlooked. 



We are all aware how defective many drawings of new species 

 are. It would be easy to give instances of works in which the 

 descriptions and figures are mutually contradictory, but at any rate, 

 when a figure is given you have something with which you can 

 compare the animal you are observing, and if you find them to be 

 quite different you should be safe in assuming that your animal is 

 distinct. 



Allowance must be made for the earliest observers, when 

 Microscopes were primitive, and it was not suspected that species 

 were so numerous as to need careful discrimination. Such allow- 

 ance has been made in establishing a number of the Miillerian and 

 Ehrenbergian species, which could not be certainly identified from 

 the simple outlines given. These pioneers were conscientious 

 observers. 



Surely moderns need not claim such indulgence now that Micro- 

 scopes have improved so greatly, and they ought to know that close 

 observation is necessary. If a man can neither observe carefully, 

 nor describe faithfull}^ nor draw accurately, surely he might leave 

 the poor beasts alone. 



It is undoubtedly the case that with the great increase in the 



