J 34 



SCIENCE- G OS SI P. 



figures are most imperfect and misleading. This 

 has in many cases led to confusion and difficulty in 

 identification, and the limitations of vision in the 

 old observers has in some instances caused mis- 

 takes in their classification, which as a whole is 

 very clear, methodical, and simple. 



Rotifera, it may not be superfluous to say. are in 

 Hudson and Gosse divided into four groups: the 

 Rhizota or fixed, the Bdelloida or creepers, the 

 Ploima or free swimmers, and the Scirtopoda or 

 skippers. Of these divisions the largest is the 

 Ploima, and this is further subdivided into illori- 

 cated and loricated. The first subdivision has six 

 families, and the second nine families. In the 

 first subdivision is placed the family Triarthradae. 

 having three genera. Triarthra, Polyarthra, and 

 Pcdctes ; also a fourth, Pteroessa, to which I shall 

 allude later. Triarthra had three species, of which 

 two, T. longiseta and T. breviseta, have carapaces, 

 or, at all events, stiff skins. Polyarthra had one 

 species, P. platiptera, which Mr. Gosse admits is 

 loricated, pointing out the line between the arms 

 as the edge of the harder part. This is a very 

 remarkable, though common animalcule, possessing 

 twelve jointed and serrated arms or blades. By a 

 powerful muscle the blades can be suddenly and 

 swiftly shot out or drawn to the sides again. This 

 is done in such a manner — so swiftly indeed that 

 the eye cannot follow the action — as to rapidly 

 propel the rotifer forwards, and so escape the maw 

 of some too enterprising enemy. The inclusion of 

 P. platiptera in the " illoricated Ploima" has lately 

 been justified by the discovery, by Mr. John Hood 

 of Dundee, of a relative which has no blades, and 

 having the integument quite flexible. This was 

 first named P. aptera, but later placed by its dis- 

 coverer in a new genus, Anarthra. This, how- 

 ever, will not justify the inclusion of Pteroessa in 

 the same family, as it was described from the 

 carapace of a dead animalcule, of which Mr. Gosse 

 saw only a single specimen, which is not a rotifer 

 at all, anrl consequently must be excluded. 



Mr. Gosse had doubts of Ehrenberg's Monura, 

 and only included it in the Coluridae out of 

 reverence for the great naturalist. It is, I under- 

 stand, an illusion. Individuals of the genus 

 Co-lurw are sometimes seen with the toes so 

 closely adhering as to appear single, and I can 

 personally vouch that the appearance is most 

 deceptive. I am told that pressure in a com- 

 pressorium will separate the toes and show the 

 rotifer to be a Colurus. The genus Diplois, of the 

 family Salpinadae, has also been disestablished, 

 and D. propatnla is now known as Euchlanis 

 propahda, owing to present inability to endorse Mr. 

 Gosse's statement that " the dorsal plate was arched, 

 ridged, and split down the middle." 



It is also known that the genus Coelopw, of the 

 family Rattulidae, was set apart from a misconcep- 

 tion as to the real shape and character of the toes, 

 probably brought about by the inferior character 



of the objective employed. Our difficulties do nob 

 end here, as a genus which is having a great deal 

 of attention given to it at the present time, Dyas- 

 chiza, is classified as Salpinadae, a family with a 

 firm and chitinous carapace. Modern methods 

 show that this is not justifiable, as, though some 

 of the species have a dorsal cleft, and all have- 

 marks which seem to indicate the edges of a 

 rudimentary carapace, in every case there is also a 

 flexible covering. In addition to this the mastax 

 or jaws, which are of great importance in all the 

 other classifications, are very far removed from 

 those of Salpinadae in character and type. Quite 

 a number of the Notommata family are now shown. 

 by careful examination to belong to this genus. 

 The very common Notommata lacinulata may be 

 quoted as an example, and Furcularia gibba of 

 Ehrenberg is another. Both these rotifers have the 

 Dyaschiza markings, and also setae on the toes. 

 Mr. Dixon-Nuttall, who has been studying this- 

 genus for several years, tells me that he considers 

 these setae as very characteristic of Dyaschiza, and 

 that he only knows of one species in which they 

 are not visible, and this may be owing to a fold of 

 skin obscuring the view. 



Mr. Gosse admitted that he had been confused 

 in the difference between Furcularia and Dyaseli iza. 

 The figures given are difficult to understand, as he 

 figures as F. gibba a rotifer which is undoubtedly 

 D. semiaperta, and as I), semiaperta a large- 

 animalcule which he said was the real " Simon 

 Pure," with a big eye in the centre of the brain. 

 This, I understand, has not been met with, though 

 carefully looked for by many microscopists. It is 

 also fairly clear that he took B. semiaperta as the 

 typical species of the genus Furcularia. It is- 

 probable that he never saw the markings on the 

 back and sides, the dorsal and lateral antennae, or 

 the setae on the toes. In addition to F. gibba 

 there are several other species of the genus that 

 will have to remove to Dyaschiza, but in the 

 majority of their cases description and figures have 

 been so vague that it is difficult to be sure of 

 identification. The same may be said of a number 

 of species of the " illoricated Ploima " that are 

 under ^th of an inch in size. 



The classification in Hudson and Gosse is so- 

 good and clear that it is not desirable to alter more- 

 than is absolutely necessary. In the matter of 

 Dyaschiza there are two courses open : either to- 

 do away with the genus, and place its species in 

 Furcularia, with which they agree very fairly well, 

 or, what seems better, owing to Dyaschiza being, 

 as Mr. Dixon-Nuttall has pointed out to me, a good 

 and well-marked group, to transfer the genus 

 from Salpinadae to the already very large family 

 Notommatadae, placing it next in order to Fur- 

 cularia, from which it will take a large proportion 

 of species. In fact, it will probably be the largest 

 genus in the family. 



1 think I have now said enough to show the 



