40'2 History of Britisli Entomosfraca. 



17^9, lie again describes it under the name of Monoc. pulex. Baker 

 in his " Employment for the Microscope," 1753, describes and 

 figures a species which is evidently the D. pulex. He maintains 

 that it has two eyes, and severely handles poor Bradley for saying- 

 it has only one ; though that is about the most correct part of that 

 author's description ! He quotes Swammerdam's memoir, and re- 

 tains his name for it as expressive of its appearance and motion. 

 Joblot, in his " Observations d'Histoire Naturelle, faites avec le 

 Microscope," 1754, describes a species under the name of " Pou 

 aquatique," which Muller quotes as his D. sima, but which Straus 

 says is not so, but is his D. macrocopus. The figures which Joblot 

 gives are very indifferent, and it is not very easy to say what spe- 

 cies they are meant to represent. Schceffer in his Memoir " Die 

 griinen Arm-polypen die geschwanzten und ungeschwanzten zacki- 

 ger Wasserflohe," 1755, describes at great length two or three 

 species, under the name of " Geschwantzen zackiger wasserfloh" 

 and " Ungeschwanzten zackiger wasserfloh," — or " water flea 

 with a tail," and " water flea without a tail ;" and this me- 

 moir is the first in which an attempt is made to distinguish dif- 

 ferent species, — the various authors whom I have quoted above hav- 

 ing all, with perhaps the exception of Joblot, described only one and 

 the same. He figures two species, the D. pulex and sima, and gives 

 a sketch only of the head of a third, which being provided with a 

 tail, has been quoted by Muller and Straus as the D. longispina, but 

 which is only a variety of the pulex. This memoir contains a great 

 deal of very interesting information with regard to these insects, 

 and having been partly translated into French by J urine at the end 

 of his work on the Monoculi, 1 shall be able to avail myself of many 

 of its details. In his " I cones Insectorum circa Ratisboniam indige- 

 norum," 1766, the same author figures the D. pulex, under the 

 name of " Branchipus conchiformis primus," and in his " Elementa 

 Entomologica," published same year, I believe, he again figures it 

 under the name of " Branchipus conchiformis." Poda, in his " In- 

 secta Musesi Graecensis," 1761, describes shortly the same species 

 under Linnseus's name Mon. pulex, and Ledermuller, in his " Mi- 

 kroskopischen Gemiiths und Augen-ergotzung," 1763, gives an in- 

 different figure of a species which is easily recognizable as the 

 same. Geoffrey, in his " Histoire abregee des Insectes," 1764, gives 

 a good many details of this genus generally, and describes a spe- 

 cies under the name of " Perroquet d'eau," which IViuller quotes 

 as his quadrangula, but which Straus quotes, and I think more 

 correctly, as the D. pulex ; and Goeze, in the " Naturforscher," 



