36 



PROTOZOA. 



the peristomial groove, and from it there radiate in all directions 

 to the periphery branching strands of protoplasm. At the periphery 

 there is a thin layer of reticulated phosphorescent protoplasm 

 immediately underlying the stout cuticle which bounds the body. 

 The nutrition is holozoic, and food vacuoles are formed. Leptodiscus 

 has the form of a flattened disc, concave on one side and convex on 

 the other. On the convex side is the mouth somewhat eccentrically 

 placed, and from the same side there is a tubular depression from 

 which projects a flagellum. The protoplasm is much vacuolated as 

 in Nodihiea, and the principal part of it is aggregated at the centre 

 of the concave or aboral side of the disc. 



l-'ic. 29. Noctilura minm-is partly after Cienkowski. N nucleus ; 

 a, single animal ; 1>, conjugation of two individuals ; c ami il, 

 swarm spores. 



Noctiluca occasionally draws in its flagella and loses its peristome 

 and enters the resting state, but has not been observed to encyst. 

 It reproduces in two ways : by binary fission and by the formation 

 of small swarmers. If by fission, the division of the nucleus and 

 central plasma is soon followed by that of the whole body. Before 

 the latter is completed the development of the peristome and its 

 organs in the new individuals begins. Individuals with two central 

 masses and two nuclei are occasionally found. The formation of 

 spores takes place during the resting state. The central plasma 

 projects slightly on the surface, and divides by a superficial con- 

 striction into two prominences. The nucleus karyokinetically 

 participates in this and future divisions. These two again divide 



