956 PROTOZOA AND OTHER ANIMALS 



from the pole of communication with the host. When this influence is 

 reduced on the commencement of molting, supernumerary tomites may 

 be produced. There are, Chatton and Lwoff stated, many examples of 

 parasites certain phases of the development of which are conditioned by 

 the molt or sexual maturity of their host. The influence may be chemi- 

 cal, absorbed substances preventing a denaturation of proteins, which 

 may be the essence of cell division. The existence, in trophoepibiotic 

 ciliates, of a trophohumoral gradient of inhibition, susceptible to analysis 

 and analogous to other types of biological gradients, is suggested. 



APOSTOMEA 



Though certain ciliates that are now included in the suborder 

 Apostomea have been known for a long time, it is only recently that 

 the group has become well known. Chatton and Lwoff ( 1935) published 

 an outstanding memoir on the Apostomea, which, they stated, is only 

 the first of three parts. This first part is a monographic study of the 

 genera and species. In the suborder, according to this account, there are 

 two families, by far the more important of which is the Foettingeriidae, 

 with thirteen genera and twenty-six species. In the Opalinopsidae there 

 are only two genera. Chatton and Lwofi^ expressed doubt that one of 

 these, Opalinopsis, really is an apostome; and the other genus, Chrom'i- 

 d'ma, was included by Cheissin (1930) in the Astomata. Kudo (1939) 

 listed the Opalinopsidae in the Astomata. 



The active, growing, vegetative phase of a foettingeriid ciliate is the 

 trophont. The ciliature is in dextral spirals. In the process of growth the 

 basal granules are spaced without multiplying. At the end of the period 

 of growth the organism may encyst, the cilia are lost, and the infracilia- 

 ture undergoes detorsion, the lines becoming meridional. This phase is 

 called the protomont. It passes into the multiplicative phase, or tomont, 

 which produces by transverse fission a variable number of tomites. The 

 tomite is a small free-swimming ciliate. The ciliary rows are more or 

 less meridional, with a tendency to turn in a spiral. There is a thigmo- 

 tactic ciliary field, consisting of the parabuccal ciliature. Chatton and 

 Lwoff maintained that the tomite represents the free-living, ancestral 

 type. In twenty-two of the twenty-six species, and possibly in the others 

 also, the tomite becomes fixed to the body surface of a crustacean, and 

 transforms into an encysted phase, the phoront. In the phoront there 



