374 



NATURAL HISTORY. 



The second sub-order comprehends Saville Kent's division of the collared monads (Choano-flagellata), 

 with individuals varying from ^ ^th to g^Vi^ 1 of an inch in length, and some of which resemble the 

 collared cells of sponges. It consists of three families. In the first the animalcules are naked, and 

 either attached or free ; the genera Monosiga, Codosiga, and Astrosiga are examples (Plate 72, 

 Figs. 1 8). The forms of the second have a lorica, which may be solitary, as in Salpingseca and 

 Lagemeca, and united in Polynseca (Plate 72, Figs. 9 18). 



In the sub-order of the Flagellatu, with a definite region for inception of food (Eustomata), the 

 most interesting examples are the genera Noctiluca and Euglena. The first is one of the greatest 

 producers of the phosphorescence of the sea. 



Noctiluca miliaris, from ^th to J^th of an inch in diameter, is peach-shaped, and has a distinct 

 meridional groove to its hyaline body. The mouth fossa is at one end of the groove, and has on one side a 



33. A, NOCTILUCA MiLiAKis B, SAME WITH BUDS (from Photograph after Brooks) ; 



C, IN SECTION. (After Huxley.) 

 n. nucleus. /, flagellum; t, tentacle; d, denticle; an, anus. 



hard projecting ridge, close to one end of which ai'ises the flagellum. Close by arises a tentacle about as 

 long as the body, and there is a rod-like induration of the cuticle, extending in a sti-aight line from the 

 aboral extremity of the groove. The endoplast is oval. They exist in countless multitudes, and their 

 greenish-silvery light is produced just underneath the cuticle in irregular flashes. They increase by 

 transverse fission, accompanied by encystment and loss of the flagellum and tentacle. Under certain 

 circumstances, the endoplast breaks up, and the protoplasmic contents of the cyst collect in one spot 

 and form by division into many minute nodular masses. These cause the cuticle to rise, and finally 

 they penetrate it and develop flagella. They become detached and swim as germs (Fig. 38). 



Conjugation is also observed. The Noctilucse live on minute floating Algse, which may be seen 

 amongst the vacuoles of the irregular endoplasm. 



CLASSIFICATION. CLASS INFUSORIA. 



ORDEII TENTACULIFERA 

 CILIATA 



Cn-IO-FLAGELLATA. 



FLARELLATA . 



Holotricha. 



Heterotricha. 



Peritricha. 



Hypotricha. 



Pantostomata. 



Choano-flagellata. 



Eustomata. 



The writings of Claparede and Lachmann, Stein and Huxley, have been used by the author ; 

 but his greatest obligations are to Mr. Saville Kent, whose excellent Manual of the Infusoria has 

 been quoted largely, and often word for word. 



P. MARTIN DUNCAN. 



