LOCOMOTOR AND PREHENSILE ORGANS 37 



into a thin cylindrical collar or cuff round the flagelliim. The collared 

 forms frequently possess attachment filaments, simple or branched, and 

 often cup-like loricge. The collared forms are generally known as the 

 Choanoflagellata. Similar flagellated collar cells are found in the group 

 of Metazoa to which the sponges belong. In many cases it appears that 

 the collar is not a cylinder, but a cuff with overlapping edges. 



A peculiar modification of the ectoplasm which facilitates locomotion 

 occurs in gregarines. These organisms are able to glide over a surface 

 without exhibiting any movements of contraction of the body by reason 

 of longitudinal ridges of ectoplasm between which a quantity of mucoid 

 material can be rapidly excreted. The excretion of this tenacious material 



Fig. 17. — Codonosiga allioides : A Colony of Collared Flagellates on a 

 Branched Filament ( x 320). (From Lang, 1901, after Kent.) 



causes the organism to be pushed forwards without any apparent move- 

 ments of the body. Similar gliding movements are often exhibited by the 

 merozoites or sporozoites of the Sporozoa. In the case of certain amoebae 

 such a gliding movement appears to be the result of constant streaming 

 of the cytoplasm from behind forwards, w^hile the ectoplasm in contact 

 with the surface remains stationary, very much as a bag of water can 

 be pushed along the surface of a table. 



ORGANS OF ATTACHMENT.— Though the majority of the Protozoa 

 are free-living organisms, certain forms are able to attach themselves 

 temporarily or permanently to objects. 



Amongst the Mastigophora there are many pedunculated forms. The 

 posterior extremity of the body is developed into a filament, by means 



