23 J. S. DUNKERLY ON OUR PRESENT 



which the food passes into a specialised area of the body which 

 functions as a month. There is no direct evidence to prove the 

 existence of this spiral arrangement of the collar, and at present 

 the suggestion remains a rather doubtful explanation of the 

 facts. 



The normal method of reproduction of the Choanoflagellata is 

 fissiparous, and, as usual in the Flagellata, by longitudinal 

 division. The nuclear phenomena during division have been 

 described in Codonosiga hotrytis by Fisch, and seem to resemble 

 that modified karyokinesis which is exhibited by Euglena. The 

 process of encystation is probably common, and it is stated that 

 the cysts may give rise to numerous small flagellate spores 

 (swarm-spores), which develop directly into the adult form. 

 Up to the present conjugation has not been observed in this 

 group of Infusoria. 



The habitat of Choanoflagellates is restricted by the fact that 

 normally they are all sessile forms. They can be found growing 

 on green filamentous Algae, such as Vaucheria ; on chain diatoms ; 

 on other Infusoria, e.g. Vorticella ; and on Rotifers, etc. As 

 regards their distribution, they are probably cosmopolitan, and 

 will be found in fresh or sea- water wherever looked for. They 

 have been recorded from most European countries. North and 

 South America and India. 



With regard to the forms and classification of these beautiful 

 organisms, mention need only be made of the chief distinctive 

 forms met with. The type described above is Monosiga 

 (Plate I., Fig. 1). A similar form, but stalked, is Codonosiga 

 (Plate I., Fig. 2). Codonocladiwni resembles Codonosiga, but the 

 colony has secondary branches forming umbels. Proterospongia 

 is an interesting colonial Choanoflagellate wdth several Monosiga- 

 like individuals embedded in a very transparent ground mass. 

 This form led Saville Kent to believe that sponges were but 

 colonies of Protozoa related to Choanoflagellates. There is 

 certainly a remarkable similarity between a typical Choano- 



