The Zoologist — October, 1867. 955 



defects which exist in the aquarium of this town. The first and greatest defect con- 

 sists in the fact that it is "a kind of open-air pond ;" and I call this exposure to the 

 open air a defect because it is not possible to regulate the temperature of the water s» 

 exposed, because it is not possible to regulate the light, and because it permits the 

 importation into the aquaria of dust,, of leaves of trees, and of cuttings of grass, Sec. 

 The second defect consists in the uncertain and intermittent nature of the supply of 

 sea-water. The third serious defect is that the sea-water pumped into the aquarium 

 is taken from the swimming-bath of the " etablissement," and this bath is filled direct 

 from the port. As the town of Boulogne is drained into the harbour, it is just possible 

 that the water may not at times be capable of supplying one of the well-known 

 requirements of most fishes, leaving " pelagic" fishes out of the question. If there are 

 any of the conditions above-mentioned which Mr. Lloyd would be desirous of securing 

 in the construction of an aquarium, his views have been singularly modified since the 

 lime when I had the pleasure of being in daily communication with him. The species 

 of mackerel to which I alluded in my letter to the 'Field' was Scomber scomber;, but 

 there were at the same time living in company with them eleven full-grown specimens 

 of Scomber pneumatica, besides some hundred and fifty other fishes of various kinds, 

 and ranging from six inches to upwards of forty inches in length, but which, from 

 their well-known greater powers of endurance, I did not think it worth while to 

 speak of. Mr. Lloyd takes exception to my statement with respect to the possibility 

 of keeping Scomber scomber permanently, and also to what I have said to him 

 privately in reference to the facility with which Hippocampus brevirostris may be 

 kept in confinement; but, whilst disputing that which I asserted broadly with regard 

 to a species, he wishes to saddle me with a similar responsibility in the case of every 

 individual of that species. This is slightly unreasonable. I may be " too hasty and 

 positive" in this matter, and those who have had more practice may be more cautious 

 in their assertions. I am willing to admit that they may have sufEcient reasons for 

 being so. I may observe that my " practice" began in July, 1856, and that I never 

 penned a line for publication until July in 1867; and for the reason that, although I 

 have long been in a position to write of what I believed could be done, I preferred 

 waiting until I could write of what I knew could be done. If, from the hundreds of 

 instances in which Mr. Lloyd has failed to keep his animals continuously, he will 

 kindly select and quote a few cases in which fishes have died owing to the absence of 

 some known condition which cannot be supplied in an aquarium, something will be 

 established. If I can have given me by anyone a single sufficient reason why any 

 ordinary fish which can live in aquaria for a month or two months (performing in a 

 satisfactory manner during that period all the functions of life) cannot be so kept for 

 a longer time, or for " the term of its natural life," then I shall very readily own that 

 I have been " far too hasty and positive." Let me add that I shall be sorry to a cor- 

 responding degree for having been so. Until this can be done, I must be excused for 

 preferring to draw my conclusions from those things which have been effected by 

 Mr. Lloyd, by myself, and by many other persons, to having my views modified by 

 the failures from unexplained causes which any person or any number of persons may 

 have experienced. The implication that Mr. Lloyd wishes to attach to my statement, 

 that certain animals can be kept indefinitely in properly constructed aquaria, is an 

 entirely unwarranted one. It might as reasonably be assumed that the promise that 

 man shall live "three score and ten years" implies that every man shall attain that 



