igog.J ^ R. E. Lloyd: Deep-Sea Fish caught by the ''Investigator.'^ 179 



If these five types are separate species in the ordinary sense of the word, they 

 must, according to some theorists, have primarily arisen each in a separate locality, 

 in adaptation to some peculiarity of that locality by natural selection from among a 

 population exhibiting minute variations, and subsequently come together to exhibit 

 the remarkable intermingled distribution obtained. This seems highly improbable. 



It seems more likely that the type v, the true Malthopsis lutea, is an established 

 species, which during a long period of stability has become widely distributed in 

 moderate depths of the seas around India. One specimen of this type was taken by 

 the " Valdivia " off the east coast of Africa. It is especially common at certain 

 points in the Andaman. Sea. Among the offspring which the menibers of the species 

 are producing are some which differ widely from their parents as regards their shape 

 and dermal ossicles, the differences being of particular kinds. Offspring, showing 

 the same kind of differences from their parents are being produced in widely sepa- 

 rate localities. Judging from the fact that the type w occurs in each of the four 

 communities, it may be assumed that it is a hardy and progressive form which is fast 

 becoming established as a new species. 



This is put forward as an explanation of the manner in which change is sup- 

 posed to be taking place. As to the cause of the change nothing can be said from 

 the evidence, except that it seems to be inherent in the organism and quite indepen- 

 dent of the conditions of environment. 



In many ways the phenomenon calls to mind that observed by De Vries in the 

 plant Œnothera, a phenomenon which that author terms "Mutation." This term 

 defines the manner in which evolution is believed to occur ; by using it one allows 

 exceptions to the rule that a parent and its offspring must be of the same species. So 

 far as I can understand it, the Theory of Mutation does not deal with the causes which 

 lead to the appearance of these exceptions, but emphasises the fact that the nature 

 of the organism is a much more important factor in their production than the external 

 conditions. 



An important part of the Theory of Mutations is the idea of characters as 

 definite units; an idea which seems to rest on the surest evidence. These fish 

 illustrate this and moreover show how some of the character units are related to one 

 another. 



It has been shown that there are two types of subopercular spine among the 

 collection, and that a particular type of spine is always associated with a particular 

 arrangement of the dermal plate ; that there are certain types in the form of the 

 disk which are quite independent of the character of the derma, for one specimen 

 (A 4) has preserved the narrow form but acquired the orderly character of the derma 

 completely, while others (C 2, C 4) have lost the narrowness but retained the disorderly 

 derma. It has also been shown that the nasal spine is quite independent of the 

 subopercular spine, for all the specimens, whatever the form of their subopercular 

 spines, possess nasal spines apprcrximately of the same size and form. This is the 

 opposite of what we might expect, for the nasal spine is a character peculiar to one 

 branch of the genus Malthopsis, while the subopercular spine in various forms is 



