48 SYNOPTIC COLLECTION. 



understand how the mouth, oesophagus, and the other 

 tubes and sacs of the digestive system originated. After 

 the food has been retained in the body for a time the 

 excrement is thrown out at a place near the mouth or 

 through the mouth itself, instead of being ejected from 

 any part of the body, as is the rule with the Amoeba. 



Reproduction takes place in this .genus by longitudinal 

 fission and by the breaking up of the body into flagellate 

 young. The researches of Messrs. Dallinger and Drys- 

 dale have shown that the phenomenon of fission in these 

 minute forms " is not a mere division of undifferentiated 

 sarcode into two parts." Before separation takes place 

 there is always a germination of the anatomical elements 

 which make the new monad complete, while in many 

 instances the fission is preceded by a suddenly induced 

 amoeboid condition. 1 



The young Monosiga globulosa S. K. (PI. 51, fig. 3) is 

 a free-swimming uniflagellate form which bears a resem- 

 blance to Monas (PL 51, fig. i). In course of time it 

 becomes stationary, as seen in fig. 4. Next, the stem and 

 collar are developed (fig. 5 is the adult), the latter being 

 the peculiar characteristic of many Flagellata but which 

 is entirely wanting in the young Monosiga and in the 

 adult Monas. It has been pointed out by Kent that this 

 collar is a film of protoplasm which can be extended and 

 withdrawn at will into the substance of the body in the 

 same way as the pseudopodia of an Amoeba. Combined 

 with the flagellum it serves as a most efficient trap for 

 obtaining food. Fig. 6 is the adult of another species, 

 Monosiga gracilis S. K., greatly magnified. The nucleus 

 is seen near the central part of the body. The process 

 of digestion is shown by the food particles colored blue 

 which are circulating through the body. In this genus 

 reproduction takes place both by longitudinal and by 

 transverse fission and also by the breaking up of the 

 body into flagellate young. 



1 Monthly Micr. Journ., XI, 1874, p. 7. 



