186 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



which are larger and more highly organised animals. 

 The last section is again divided into several groups, three 

 of which — the Trematodes, the Cestodes and the Nema- 

 todes — contain important hsh parasites. Representa- 

 tives of all these various kinds of parasites have been 

 investigated during the year by Mr. Johnstone in the 

 diseased fishes sent to the Laboratory. 



There is another subject sometimes discussed at 

 present in connection with iish diseases, viz., cancer in- 

 vestigation. It has been shown in Dr. Bashford's Report 

 of the Imperial Cancer Research Fund (July, 1904) that 

 cancer is found in practically all groups of the verte- 

 brata, from the fishes up to man. In all these cases, as 

 has been shown by the minute biological investigations of 

 Farmer, Moore, and others, there are cells which in place 

 of behaving like ordinary tissue-cells when they divide, 

 undergo the processes which are characteristic of egg- 

 cells when about to develop into embryos. The cancer 

 may, in fact, in the light of these observations, be 

 regarded as a new individual growing in an abnormal 

 position and causing b}^ its growth a disorganisation of 

 the tissues in which it lies. 



From the wide biological point of view it would seem 

 to be a fruitful line of investigation to determine what 

 there is in common between man and the lower animals 

 that can determine these abnormal growths. The cells 

 with the property of reproducing to form new individuals, 

 either normally or abnormally, are, of course, present in 

 both — and not in vertebrates alone, but in all animals 

 and all plants, but that is not enough to explain the 

 matter. These cells may no doubt be the pre-disposing 

 cause, but it must be obvious that an exciting cause is 

 also necessary. What exciting cause, then, can be found 

 common to those cases in all vertebrata, where the repro- 



