CRUSTACEANS pigment, called the eye-spot. What may be its precise function is not perhaps precisely known, but if that function be not visual the species of Monospilus must be blind, for they have the eye-spot, but apart from that they have no eye. In Mr. Scourfield's various papers many interesting observations are given on the species above enumerated. It would take up too much space to give adequately even a summary of all this valuable information, but attention may be called to one branch of his researches which may be regarded as exceptionally important. In a paper on Leydigia acantho- cercoides (Fischer), a species closely related to L. quadrangular^ (Leydig), he says : ' There seems no room for doubt at the present day that the production of winter or resting eggs is of universal occurrence among the little animals belonging to the Crustacean sub-order Cladocera, not- withstanding the fact that in many species such eggs have not yet been observed. In the most representative family, the Daphnidas, these special eggs are always enclosed in a very remarkable and complex modification of the shell of the mother, commonly known as the ' ephippium,' because of its resemblance to a saddle both as regards shape and position. In the other Cladoceran families the production of an ephippium, similar in all respects to that found among the Daphnida?, is extremely rare, the only certain instance, so far as I know, being Macrothrix spinosa, King, recorded by Professor G. O. Sars in Additional Notes on Australian Cladocera raised from Dried Mud. Nevertheless structures clearly homologous to true ephippia, though usually very much simpler, are found in the families Bosminidae, Lyncodaphnidae and Lynceida?. The species belonging to the remaining families of the Cladocera appear to allow their resting eggs to escape freely into the water without providing them with any auxiliary coverings.' ' Mr. Scourfield then proceeds to point out that already in 1820 Jurine ' distinctly refers to the saddle or ephippium in the case of Cbydorus sphcericus, that Schodler in 1846 records of Eurycercus lamel- fatus, ' that a number of winter eggs were deposited at one time in the almost unmodified cast shell of the mother, a fact which has since been confirmed by Weismann,' that by Kurz in 1874 protective coverings for the winter eggs were reported ' in some sixteen species belonging to the genera Camptocercus, Alona, Plearoxus, Chydorus, etc.,' and that slightly later, in 1 877, ' Weismann independently discovered the resting eggs of several species of the same family ' [Chydoridas], while since that time ' the resting eggs of many other species have been alluded to, in more or less detail, by various writers.' In an earlier paper Mr. Scourfield says : ' Compared with the highly evolved " ephippium " which is formed by the Daphnidz for the protection of their resting eggs, the arrange- ment in Cbydorus spbcericus (and other species of the Lynceidse) is manifestly very primitive, and although both are fundamentally the same I would suggest that the simpler structure be distinguished as a proto- 1 Journal ef the Quekett Microscopical Club, vol vii. p. 171 (1899). 215
