6o 



FROTOZOA 



common network. This is due to the fact that one of the two 

 daughter-cells at each fission, that does not retain the parent shell, 

 remains in connexion with its sister that does : sometimes, how- 

 ever, it retracts its pseudopoclia, except two which become flagella, 

 wherewith it can swim off. The test of Pamphagus is a mere 

 pellicle. In Lieberkilhnia (Fig. 12) it is hardly that; though 

 the body does not give off the fine pseudopodia directly, but emits 

 a thick process or " stylopodium " l comparable to the protoplasm 

 protruded through the pylome of its better protected allies ; and 

 from this, which often stretches back parallel to the elongated body, 



Fig. 11. Microgromia socialis. A, entire colony ; B, single zooid ; C, zooid which has 

 undergone binary fission, with one of the daughter-cells creeping out of the shell ; 

 D, fiagellula. c.vac, Contractile vacuole ; nu, nucleus ; sh, shell. (From Parker 

 and Haswell, after Hertwig and Lesser. ) 



the reticulum of pseudopodia is emitted. Diaphorodon has a 

 shell recalling that of Difflugia (Fig. 10, D, p. 55), formed of sandy 

 fragments, but with interstices between them through which as 

 well as through the two pylomes the pseudopodia pass. In all 

 of these the shell is formed as in the Khizopods once for all, and 

 does not grow afterwards; and the fresh-water forms, which 

 are the majority, have one or more contractile vacuoles ; in 

 Allogromia they are very numerous, scattered on the expanded 

 protoplasmic network. 



The remaining marine families may all be treated of generally, 

 before noting their special characters. Their marine habitat 

 is variable, but in most cases restricted*. A few extend up the 

 brackish water of estuaries: a large number are found between tide- 



1 This convenient name is due to my friend Dr. A. Kemna of Antwerp. 



