PHYSIOLOGY OF SEX AND REPRODUCTION. 235 



few sea-urchins, the depressions in the skin in one or two sea- 

 cucumbers, the modified tentacles of some marine annelids, the dorsal 

 shell-chamber in water-fleas, the incurved abdomen of higher crusta- 



FlG. 01. — The Sea-horse (Hippocampus guttuiatus). — From 

 the Atlas of the Naples Aquarium. 



ceans, the gill-cavities of bivalves, the beautiful brood-shell of the 

 argonaut, illustrate a habit even an outline of which is beyond our 

 limits. 



Fig. 92. — The female of the " Paper Nautilus (Argonauta argo), 

 with its brood-chamber. — After Leunis. 



X. Nemesis of Reproduction. — We have already shown how 

 reproduction in its origin is linked to death. The primitive ruptures 

 by which the protozoon reduces encumbering bulk, saves its own life, 

 and multiplies its kind, are only a step or two from more diffuse 

 dissolution which is death. 



The association of death and reproduction is indeed patent enough, 

 but the connection is in popular language usually misstated. 



