June 27, 1912] 
NATURE 
425 
we usually say that the forcing influence ought to be 
in tune with the natural frequency of the system. In 
every case the natural q is ¥n*—f?, but we find the 
critical g to be either n or ./n?—2f*. k 
This is probably known to mathematicians, but it is 
certainly not known to electrical engineers; it is a 
most important matter for people engaged in telephony, 
and especially for persons engaged in wireless signal- 
ling. Joun Perry. 
Inheritance of Paternal Characters in Echinoid Hybrids. 
In the Journal of the Marine Biological Association 
for October, 1911, we published a *‘ Preliminary Notice 
on the Experimental Hybridisation of Echinoids.”’ It 
comprised the results up to date of an investigation 
which had been carried on at the Plymouth Labora- 
tory during 1909, 1910, and igi1. The forms experi- 
mented on were Echinus esculentus, E. acutus, and 
£. miliaris. Certain characters were studied in the 
hybrids, which appear in the late larve and 
do not vary in the parental forms. As the result of 
three years’ work, we came to the conclusion that 
the inheritance of these characters was always strictly 
maternal. 
The work has been repeated this year, but our 
results differ from those of previous years in several 
important points. It may, therefore, be of interest 
to other workers in this field if we give a brief state- 
ment of these new results at once. 
The outstanding feature of this year’s investigation 
has been the fact that EF. miliaris eggs, when fer- 
tilised with their own sperm, have only been raised 
with great difficulty to a late stage. In previous 
years this species has always grown more healthily 
and developed more rapidly in the laboratory than 
either E. esculentus or E. acutus. This fact, we have 
suggested in our preliminary paper, is possibly due 
to E£. miliaris being a shore form, the conditions of 
growth in the laboratory being more favourable to 
it than to the other species, which are deep-water 
forms. This year, however, E. miliaris has developed 
less readily under laboratory conditions than E. escu- 
lentus, E. acutus, or any of the hybrid crosses. 
Evidently some condition of the environment which 
Was not present in previous years has affected the 
germ cells of E. miliaris this season. 
Hybrids between E. miliaris ¢ and E. esculentus 
and E. acutus Q were obtained this season with ease 
and were, as before, strictly maternal. The crosses 
with E. miliaris 2, on the other hand, could only be 
made with the greatest difficulty. Probably, then, it 
is the eggs and not the sperm of E. miliaris which 
are at fault. The hybrid larve in all the cultures of 
the cross E. acutus d x IE. miliaris 2 turned out 
to be strictly paternal and not maternal, as in previous 
years. With one exception all the cultures of E. 
esculentus 6 X E. miliaris 2 have also been paternal 
with regard to the inheritance of the posterior ciliated 
epaulettes and the green pigment masses. The E. 
miliaris egg this year seems to be unable to transmit 
its characters to the hybrid offspring, as in previous 
years. The exception mentioned above was in the case 
of the only cross between E esculentus ¢ and E. miliaris 
9, in which a large percentage of the eggs fertilised. 
In cultures from this fertilisation the hybrids were 
maternal with regard to the above-mentioned char- 
aeters. Thus in the only hybrids with E. miliaris 2, 
in which a large number of the eggs fertilised, we 
found the usual maternal inheritance. 
CRESSWELL SHEARER, 
Watter De Morcan, 
H. M. Fucus. 
Laboratory of the Marine Biological Association, 
Plymouth, June 22. 
No. 2226, vor. 89] 
Taste or Smell in the Laughing Jackass (Dacelo). 
WHEN experimenting on the palatability of insects, I 
have often noticed that birds appear to be able to 
tell whether an object is nice or nasty by merely hold- 
ing it between the extreme horny tips of the bill. 
From this observation I inferred that actual contact 
with the tongue or soft palate was unnecessary for 
the purpose. 
A case came under my notice to-day, however, which 
not only strengthened this conclusion, but suggested 
| that some birds at all events are able to ascertain 
| the distastefulness of some insects without actually 
pecking them. I offered the larva of the small Eggar 
moth (Eriogaster lanestris)—a velvety black hairv 
grub, ornamented with brown spots and yellow streaks 
—to a laughing jackass (Dacelo cervina). The bird 
was preparing apparently to take it, but when the tip 
of his beak was about an inch away, he drew back 
his head and shook it, and opened and shut his beak, 
exactly as I have seen birds do when tasting an un- 
pleasant flavour. Every time the caterpillar was pre- 
sented to him he behaved in the same way, and 
nothing would induce him to touch it. I repeated 
the experiment with two examples of Dacelo leachii 
and Dacelo gigantea, with precisely the same result. 
The birds’ behaviour so forcibly suggested a keen 
olfactory sense that, despite the distance the larva 
was held from their nostrils, and despite the usually 
accepted belief that the sense of smell is defective or 
absent in most birds, I do not know how to emend 
| the keeper’s remark, ‘‘ They don’t like the smell of it.” 
It appeared to me, indeed, that they ‘‘ smelt” the larva 
with the mouth, if such an expression may be used, 
and considering the intimate connection in ourselves 
between taste and smell, I think this explanation is 
possibly correct, although to me the larve individually 
have no appreciable scent. 
A large number of the larvae of fhis moth were sent 
to me for experiment by Mr. F. C. Woodforde, and 
I was able to try them with many species of birds. 
There is no doubt that they are, on the whole, un- 
palatable, but not very highly so. Some of the birds 
refused to touch them, others pecked them once or 
twice, others persevered for a long time, beating and 
shaking them about on the ground, generally giving 
them up in the end, but in one or two cases eating 
the mangled remains. None, however, behaved to- 
wards them as the laughing jackasses did. 
Zoological Society, June 16. R. I. Pocock. 
Rearing Asterias rubens, L.—Larve with Double 
Hydrocele. 
THe note may be of interest that some young 
Asterias rubens have recently completed their meta- 
morphosis here, while others are at present in the 
stage of sucker fixation. 
The successful culture was one of several made by 
me in April last at the Millport Marine Biological 
Station, from a good supply of healthy starfish put 
at my disposal by the Superintendent of the station. 
All the cultures were taken up to Glasgow that same 
evening, and two days afterwards the swarming larve 
were transferred to small vessels holding about half a 
gallon of sea water and provided with an arrange- 
ment for securing gentle and continuous internal cir- 
culation. 
In a week or so, the larvee were fed with a culture 
of Nitschia. Two weeks afterwards a considerable 
| number from the best jar were transferred to a second 
hatching vessel, and, a fortnight later, selected 
specimens from these were brought into a third vessel 
of the same type. The result was thus obtained with 
an expenditure of about two gallons of sea water, 
although a good deal more was actually employed in 
