272 NATURAL SCIENCE [October 
Some prejudice attaches to the habit of existence in which these 
creatures indulge. On the other hand, the Parasite in Lucian 
maintains that his profession and personality are the true charm 
and glory of social life. The parasite in zoology may urge in its own 
favour that it is an eminent preacher and teacher of cleanliness, and 
an unanswered advocate for the theory of evolution. The family 
Choniostomatidae is at present divided into six genera. Forty-five 
species are known, chiefly through Dr Hansen’s researches. The 
first published, however, was Sphaer onella leuckarti, described by 
Salensky in 1868. Thus, so far as their history is known, it is open 
to suppose that the whole batch has been specially created within the 
limits of the present century. But the reverential motive which 
prompts hypotheses of that kind is surely undermined when they 
require us to contemplate one set of crustaceans as specially contrived 
to live and multiply, and another set of crustaceans as specially 
contrived to be vampyres on the first set, and to stop them from 
breeding. The latter strange effect produced by the presence of some 
crustacean parasites on their crustacean hosts was first expounded by 
Prof. Giard. Dr Hansen finds reason to believe that, as a rule, with 
the exceptions to which all rules are lable, the Choniostomatidae 
prevent their entertainers from rearing a family. With the opinion 
advanced by Giard and Bonnier in regard to the Epicaridea, that each 
parasite has its particular host, and is found on no other species, he 
does not fully agree, and he also adduces evidence to show that such 
a rule is not applicable to the whole of the present group. Certain 
members of it have been discussed by the French authors just 
mentioned, and some of their results are subjected to rather severe 
criticism. This, amid the intricacies of a new subject, will be highly 
acceptable to the general reader. Apples, for choice, need a subacid 
flavour. They must not be so sharp as to set one’s teeth on edge. 
As the eminent authors reciprocally compliment one another in the 
names of the new species, there is evidently here no very desperate 
quarrel. By the extraordinary patience with which during several years 
Dr Hansen has been accumulating his observations he is entitled to be a 
little intolerant of more rapid methods, whichcannot fail to be hazardous 
in a material so difficult. The remark which he quotes on his title-page, 
“We want facts, not inferences, observations, not theories, for a long 
time to come,” is from Watural Science itself, so it must be true, and a 
paragraph of his own, beginning, “ Now-a-days many authors have a 
remarkable weakness for publishing innumerable immature notes,” 
deserves cosmopolitan circulation. In another passage Dr Hansen 
says, “I confess that, though I honour everybody who is capable of 
suggesting a theory which proves to be well founded and fertile in 
results, I have always felt, and, as time goes on, feel more and more 
distaste for superficial conjectures.” But this is almost like saying, 
“There are too many anglers ; what we want is fish.” People will go 
on angling to please themselves, without regard to what we want. 
Allowance must be made for differences of temperament and taste. 
Some misguided persons hear of the discovery of new families, genera, 
and species with a stolid want of enthusiasm. They perhaps for 
their part think nothing important but the course of the nerves or 
the action of the hepatopancreas. Mr Henslow dismisses the origin of 
