88 THE LOBOSA 



Plastogamy. A process of the temporary or permanent fusion 

 of two or more individuals has been observed by Schaudinn (27) 

 in Centropyxis, and by Zuelzer (35) in Difflugia urceolala, and probably 

 occurs in other Thecamoebida. In Centropyxis two individuals may 

 join together plastogamically and produce a daughter individual 

 with two nuclei and two chromidial networks, or if three individuals 

 join together they produce a daughter individual with three nuclei 

 and three chromidial networks. In some cases, the daughter 

 individual produced by the plastogamy has an abnormal shell and 

 the two nuclei and chromidial networks fuse together. In other 

 cases, again, only one of the individuals gives rise to a daughte^ 

 individual, and that is of the normal type. 



In Difflugia urceolata a process of plastogamy occurs in which the 

 nuclei and chromidial networks remain passive, when external con- 

 ditions become unfavourable, but this appears to be antecedent only 

 to disintegration. In the autumn, however, the protoplasm of one 

 of the two participants in a plastogamic union passes into the shell 

 of the other, and more rarely a process of plastogamy occurs in which 

 the nuclei and chromidial network of both individuals are active, but 

 definite fusion of nuclear elements has not been observed. At the 

 end of this plastogamic fusion the empty shell may become firmly 

 fixed to the shell containing the fused individuals, giving rise to 

 the twin-shells so often found in cultures of these creatures 

 (Rhumbler [22]). The meaning of the different forms of plasto- 

 gamy in the Thecamoebida is not clear, but there is no evidence at 

 present that they represent any phase of the true sexual process. 



The only observation of a true conjugation in the order is that 



described by Schaudinn, in which 

 definite heterogametes are formed 

 and conjugate (p. 77). 1 



Family COCHLIOPODIIDAE. Tests 

 usually thin and supple, with a 

 flexible margin, shaped like a cap, 

 limpet shell, or helmet. Pylome 

 widely open. 



The genera included in this family 

 have close affinities with some of the 

 Gymnamoebida. The shell is not 

 perforated by the pseudopodia, but in 

 Fio ig Cochliopodium it often assumes many 



nm penuddum, Hert. and diffe rent shapes according to the 

 Less, a, nucleus, surrounded by a halo of conditions of the animal, and in some 



species usually attributed to the genus 

 (G. actinophorum and C. digitatum) it 

 entirely surrounds the body and is perforated by the pseudopodia, the 



1 See Note, p. 93. 



