August 21, 1891.J 



SCIENCE. 



107 



The life of the tropics, so far as the fishes are concerned, 

 offers analogies to the life of cities, viewed from the stand- 

 point of human development. In the same way, the other 

 regions under consideration are, if we may so speak, a sort 

 of ichthyological backwoods. In the cities, in general, the 

 conditions of individual existence are most easy, but the com- 

 petition is most severe. The struggle for existence is not a 

 struggle with the forces and conditions of nature. It is not 

 a struggle with wild beasts, unbroken forests, or a stubborn 

 soil, but a competition between man and man for the oppor- 

 tunity of living. 



It is in the cities where the influences which tend to the 

 modernization and concentration of the characters of the 

 species, the intensification of human powers and their adap- 

 tation to the various special conditions, go on most rapidly. 

 That this intensification is not necessarily progress, either 

 physically or morally, is aside from our present purpose. 



It is in the cities where those characters and qualities not 

 directly useful in the struggle for existence are first lost or 

 atrophied. Conversely it is in the "backwoods," the region 

 most distinct from human conflicts, where primitive customs, 

 antiquated peculiarities, and useless traits are longest and 

 most persistently retained. The life of the backwoods will 

 be not less active and vigorous, but it will lack specializa- 

 tion. 



It is not well to push this analogy too far, but we may 

 perhaps find in it a suggestion as to the development of the 

 eels. In every city there is a class which partakes in no 

 degree of the general line of development. Its membei's are 

 specialized in a wholly different way, thereby taking to them- 

 selves a field which the others have abandoned, and making 

 up in low cunning what they lack in strength and intelli- 

 gence. Thus among the fishes we have in the regions of 

 closest competition a degenerate and non-ichthyized form, 

 lurking in holes among rocks and creeping in the sand, 

 thieves and scavengers among fishes. The eels fill a place 

 which would otherwise be left unfilled. In their way, they 

 are perfectly adapted to the lives they lead. A multiplicity 

 of vertebral joints is useless to the typical fish, but to the eel 

 strength and suppleness are everything, and no armature of 

 fin or scale or bone so desirable as its power of escaping 

 through the smallest opening. 



It may be too that, as rovers in the open sea, the strong 

 swift members of the mackerel family find a positive advan- 

 tage in the possession of many vertebra?, and that to some 

 adaptation to their mode of life we must attribute their lack 

 of ichthyization of the skeleton. But this is wholly hypo- 

 thetical, and we may leave the subject with the general con- 

 clusion that with the typical fish advance in structure has 

 specialized the vertebrae, increased their size and the com- 

 plexity of their appendages, while decreasing their numbers; 

 and that, with some exceptions and modifications, this re- 

 duction is characteristic of fishes in the tropics, and that it is 

 so because in the tropics the processes of evolution are most 

 active, so far as the fishes are concerned. 



LETTERS TO THE EDITOR. 



** « Correspondents are requested to be as brief as possible. The vrriter''s name 

 is in all cases required as proof of good faith. 



Oil request in advance, one hundred copies of the number containing his 

 communication wilt 'le furnished free to any correspondent. 



The editor will be glad to publish any queries consonant with the character 

 of the journal. 



Fair-Weather Echoes. 

 My dog, a deep-voiced Neivfoundlander, has one plague in life 

 — an echo. It comes from a cottage some three hundred yards 

 off, and there that " other dog" wUI always have the last word. 



This is exasperating, and ' ' Graph " — he is named after another 

 sound-producer, the graphophone — gives vent to his anger in a 

 series of short, sharp, threatening yelps, which are of course more 

 distinctly reproduced than the long bow-wows and howls. Last 

 night Graph was very noisy, but the echo was silent. I tried to 

 rouse it, and excited Graph to do his utmost, but with no effect. 

 A moderate, evendown rain was falling, and the fair-weather 

 echo would not venture out. There is, of course, a reason for 

 this, but I had never noticed the fact before. Is the explanation 

 that the lines of rain cut through the aerial sound-waves and 

 stop them ? Are echoes among the hills interfered with by 

 rain ? 



When the shower was over I tested the echo again, and there it 

 was, a little fainter than usual, but persistent as ever. 



A. M. B. 



Colonial Beach, Va., Aug. 13. 



Number of Words in an Ordinary Vocabulary. 



In examining the vocabularies of children, my interest in the 

 size and nature of the vocabulary of an ordinary person, previ- 

 ously aroused by the varying statements and estimates I have 

 seen, was excited sufficiently to induce me to spend a portion of 

 my vacation in making some investigations, the results of which 

 may be of interest to the readers of Science. 



I first turned to Webster's Unabridged Dictionary (edition of 

 1870), and counted the words on every twenty-fifth page, and 

 found the percentage of them whose meaning was known to me. 

 Then by calculation I found that if the same percentage holds for 

 the other pages I must know the meaning of nearly seventy thou- 

 sand of the words given in that edition of the dictionary. Since 

 in the dictionary a word as a transitive verb, as an intransitive 

 verb, as a noun, as an adjective, as an adverb, is separately de- 

 fined, as well as when used with a prefix, a suffix, or in a com- 

 pound; and since the irregular plurals, adjectives irregularly 

 compared, and the parts of irregular verbs are also given, this 

 number is perhaps twice that of the really different words. The 

 meaning of some of tbese words was readily divined from their 

 form, although they had never been seen. On the other hand, 

 one word not unfrequently has a dozen different shades of mean- 

 ing, several of wliioh often require as different and definite asso- 

 ciations as entirely distinct words. Hence the effort required .to 

 learn all of these words, with their different shades of meaning, 

 but similar form, is probably as great as it would be to have sev- 

 enty thousand different words, each having but one meaning. I 

 did not understand the meaning of all of the words well enough 

 to define and use them with accuracy,, but merely well enough to 

 grasp their meaning in any sentences in which they might be used, 

 and I probably have never actually used a fourth of them. But, 

 besides the words in the dictionary and some new words given in 

 later editions, and a number of words and phrases from other lan- 

 guages in common use, there are probably several thousand proper 

 names, such as are found in history, geography, fiction, and 

 among acquaintances, each with its distinct associations, famihar 

 to every intelligent person. These words will more than make 

 up for any error in counting that I could have made. 



Professor E. S. Holden (Trans. Philol. Soc, 1877), found his 

 own vocabulary to be between thirty-three and thirty-four thou- 

 sand words, and estimated that of an ordinarily intelligent person 

 at twenty-five thousand. I do not know what he called a word, 

 nor whether he counted as known words that he could not or did 

 not use. He estimates that the vocabulary of technical terms 

 possessed by a specialist may reach ten thousand or more. In 

 " Gray's Structural Botany " there is a glossary of between two 

 and three thousand technical terms, the vast number used in 

 cryptogamic botany not being included in the list, and of course 

 none of the special names of plants, so it is not improbable that a 

 well-read botanist may have a technical vocabulary of ten thou- 

 sand words, and a zoologist a greater number. 



The words in common use by the ordinary individual has been 

 estimated at from one to three thousand, and it is claimed that 

 when one has learned the meaning of that many words he can 

 carry on any ordinary conversation or understand common, gen- 



