PLATE M. 



] Fig. 1. Daphnia schceferi, post-abdomen of female. 



Fig. 2. " '' - "male. 



Fig. 3. " " male antennule. 



Fig. 4. " " brain and nerves. 



inf. ce. g. infra-oesophagal ganglion with nerves to anten- 

 nae; ce. oesophagus; n f. frontal nerve; g. opt. optic gang- 

 lion; ra. opt. muscles which move the eye; p. f. pigment 

 fleck; n. opt. optic nerve. 



Fig. 5. Daphnia scha'fferi, posterior part of embryo. 



- Fig. 6, Eiirycercus lamellatus, heart, showing the anterior bifid 



portion between the lobes of which is the arterial opening 

 and valve. The vaned arrows represent deeper currents 

 while the unvaned indicate superficial ones^ The dotted 

 line represents the position of the pulsating membrane 

 separating the venous from the arterial currents and seen 

 in section at (a). 



- Fig. 7. Daphnia similis, anterior part of the nervous system seen 



from below, a. optic nerve; b. optic ganglion; c. Irontal 

 nerve; d. nerve to antennules; e. commissure connecting 

 upper and lower oesophagal ganglion; f. nerves to antennae 

 and mandibles. 



