Marcu 21, 1884.] 
of Rosse, the Earl of Crawford and Balear- 
res, Drs. Wagner, Schjellerup, Ball, and Back- 
lund, and Professors Klinkerfues and Bredicton. 
American astronomers have also done their 
full share ; papers having been contributed by 
Dr. Peters, and Professors Pickering, Holden, 
Todd, Wright, and Stone. We express the 
hope that Copernicus, as a high-class journal 
for the publication of astronomical papers, may 
at some future time be re-issued under the 
same management as before. 
LETTERS TO THE EDITOR. 
*.* Correspondents are requested to be as brief as possible. 
The writer’s name is in all cases required as proof of good faith. 
‘Tilusive memory.’ 
THE subject presented in Science for March 7 (p. 
274) under the above heading, by Mr. Osborn, if an 
obscure, is certainly an interesting problem in psy- 
chology. Its scientific treatment, however, will prob- 
ably require a much wider range of investigation 
than that proposed by the writer. He has indicated 
“two widely different theories ’ in explanation of the 
mental phenomenon: a third hypothesis appears to 
_ have escaped him. 
Plato, as is well known, recognized this peculiar 
condition of the mind, and made use of it as an evi- 
dence of pre-existence,—a fancy embodied in the 
familiar lines of the poet: — 
‘** Our birth is but a sleep and a forgetting: 
The soul that rises with us, our life’s Star, 
Hath had elsewhere its setting, 
And cometh from afar: 
Not in entire forgetfulness, 
And not in utter nakedness, 
But trailing clouds of glory, do we come.” 
If, now, we substitute for Plato’s conception of an 
individual personal experience the more prosaic one 
of ancestral experience, we shall have, brief, the 
third hypothesis, — the partial continuity of conscious- 
ness through genetic descent, instead of through me- 
tempsychosis or transmigration. From this aspect, 
the problem of the irreferable impressions of vague 
reminiscence would not fall under the class of erin- 
nerungs-tduschung, or ‘ illusive memory,’ at all. 
The modern reference of all the varied ‘ instincts’ 
of animal life to the simple physiological datum of 
the heredity of a limited experience and memory, 
would naturally lead us to anticipate some such ex- 
hibition in the human race; nay, rather to wonder 
why we do not find such experiences much more pro- 
nounced and abundant. Notwithstanding the enor- 
mously greater expansiveness of cerebral action in 
man than in his lower fellow-creatures, the long- 
continued or reiterated impressions of a far-reaching 
ancestry would seem to justify the induction that 
‘intuitions ’ (so precious to the metaphysician) should 
be manifested in particular channels in a much 
stronger and more decisive form than we actually 
observe. Here, then, is a negative psychologic prob- 
lem calling for explanation, and well deserving a 
careful comparative investigation. 
To satisfactorily test this ‘third hypothesis’ is 
undoubtedly an extremely difficult undertaking, both 
by reason of the usual ‘haziness’ of these Platon- 
SCIENCE. 345 
ic reminiscences, and of the rare opportunities of 
authentie verification of special parental or aval rec- 
ollections. The question, however, is one of such 
biologic importance, that it merits an even laborious 
research; and, if in only one or two instances a clear 
evidence of such transmitted memory in man could be 
established, it would justify the inference that many 
similar cases are referable to the same principle. 
The inquiry should include the antecedent experi- 
ences of grand-parents as well as of parents: since 
there is reason to believe that aval heredity is relative- 
ly more frequent than direct parental heredity; or, 
in other words, that there is a tendency to ‘ alternate 
generation ’ running through the animal kingdom. 
Washington, March 13. Wiebe oF 
‘The oldest living type of Vertebrata,’ 
Chlamydoselachus. 
In Science, No. 57, p. 275, my friend, Professor 
Cope, falls into the error of placing among the species 
of the genus Diplodus Ag. (re-named Didymodus by 
Cope) the ‘ peculiar selachian’ recently discovered, 
and described by me in these columns. With the 
specimen before him, he would be the last man to 
make such a mistake. And no doubt he will thank 
you for giving the space necessary to a correction. 
The most important of the characters on which the 
genus Diplodus was founded by Agassiz (18438, Pois- 
sons fossiles, iii., pp. 204, 209), that by which it is 
separated from Hybodus, Sphenonchus, and Clado- 
dus, is a greater development of the secondary cones 
of the teeth, while the median cone remains rudi- 
mentary or comparatively undeveloped. ‘This is not 
the case with Chlamydoselachus: it is not the secon- 
dary, but the median, cone in which is found the 
greatest development; agreeing in this respect with 
Agassiz’ genera Hybodus, Sphenonchus, and Clado- 
dus, in which ‘* le e6ne médian l’emporte sensiblement 
sur les cénes latéraux, et se développe en quelque 
sorte Aleur détriment.’’ In theteeth of Chlamydose- 
lachus, the cone at either side of the median is a mere 
rudiment, If the new selachian was to have been 
placed in either of the fossil genera mentioned, it 
should have been Cladodus. Mr. Cope says of Didy- 
modus, ‘The species possess two, three, or four den- 
ticles.’ Of course, a second thought will increase 
the number so as to include Chlamydoselachus, which 
has more than four. 
The propriety of placing living species in fossil 
genera of so long ago on account of resemblances in 
a single organ, such as a tooth only of a selachian, is 
to be questioned. The teeth do not give satisfactory 
clews to structure and shape of other organs, or of 
the body itself, in the majority of the sharks and 
skates. This is evident enough on comparison of the 
teeth of Carcharias, Alopias, Zygaena, Squatina, Tor- 
pedo, Scyllium, Raja, Triakis, Disceus, Mustelus, 
Trygon, Pristis, Potamotrygon, Rhinobatus, Dicero- 
batus, and others. It would be hardly worth the 
while to separate recent genera by the number and 
position of fins, or shape of body, and then make them 
equal to the same fossil genus on account of some 
similarity in teeth. Material in my possession will 
enable me, as soon as the necessary drawings can be 
made, to prove conclusively that Chlamydoselachus 
does not belong to the genus Didymodus of Cope 
(= Diplodus Ag.), and that it was hardly safe to 
announce Didymodus as the ‘oldest living type of 
Vertebrata’ until more was known about Chlamydo- 
selachus, S. GARMAN. 
Cambridge, March 17. 
