Hydatinaea.] TH E INFUSORIA. 351 



genera. Thepropagative system is distinctly hermaphroditic 

 in fifteen genera. The ovarium, which only evolves a few 

 large ova at a time, is mostly ovate : in Notommata 

 myrmeleo, clavulata, and in Diglena lacustris, it is very 

 long. It communicates, by a short oviduct, with the 

 alimentary canal near its termination. None of the species 

 are viviparous. The male organs, when present, consist 

 of two filiform, extended, wedge-shaped glands, and a con- 

 tractile vesicle. The egg is worthy of notice, having 

 sometimes a smooth soft shell, at others a hard spinous 

 one ; the latter is termed the winter ovum, and considered 

 by M. Turpin as constituting the genera Bursella and Eri- 

 thrinella (?) of plants. In eleven genera, a vascular system, 

 composed of transverse and longitudinal vessels, a cervical 

 net-work and free tremulous organs, like gills, with respi- 

 ratory tubes or openings in the neck, is observed. The 

 system of sensation is indicated by the presence of eyes, 

 mostly red, with a ganglion beneath them ; these organs 

 being anterior upon the edge of the upper surface of the 

 body, or in the neck opposite to the mouth, indicate the 

 back or dorsal surface of the animalcule ; also nerve-like 

 fibrilla3 exist in several species of Notommata, Diglena, 

 Enteroplea, Triarthra, and especially in Hydatina. Some 

 species of Synchaeta evolve light and give rise to the 

 phosphorescence of the sea. Hydatina senta, Diglena 

 catellina, and Triarthra, are sometimes so numerous as to 

 render the pools of water in which they reside milky and 

 turbid. 



