270 Chronicles of Science. [April, 
Ailantus glandulosus, the tree on which the Bombyx cynthia worm 
feeds. This species is the only one with which there is any chance 
in Great Britain, and accordingly it was the one chosen for culti- 
vation. After the trees had grown up, the eggs were obtained and 
hatched, and the process of feeding and growing went on finely. 
At length the cocoons were obtained ; and now came the question, 
What is the value of the cocoons when you have got them? To 
this the answer is indeed very disappointing. They are the least 
in value of any silkworm’s cocoon, and are in fact almost rubbish. 
They do not give a continuous thread of one or two thousand yards, 
as does the Bombyx mori; no, nor even of one or two yards: like 
cotton, they have to be carded. And this being done, it was found 
after a year or two that the estate yielded about ten shillings per 
acre; by great good fortune, the next year it yielded eight, while 
potato-fields yielded twenty pounds; and then, much to the relief 
of the unhappy silkworm-cultivator, a good sharp frost killed off 
his Azlanti and Bombyces, one and all, in the same night. Silk- 
worms are all very well as toys or entomological specimens, but in 
Britain they are commercially a failure. 
Polymorphism among Corals——The name “ polymorphism” 
among animals has been applied to the phenomenon which consists 
in the co-existence of two, three, or more forms of a species, each 
serving some appropriate function for the benefit of the species 
collectively. In males and females, we have the ordinary case of 
“dimorphism ;” in the males, females, and neuters of bees we have 
a case of polymorphism, which might be designated trimorphism. 
Among the great ants of South America, Mr. H. W. Bates has 
described a case in which, besides males and females, there are 
three forms of workers. In the Ccelenterata, polymorphism is 
well known by striking examples among the Hydrozoa,—the 
various individual polyps which make up a_polypary having 
often different forms in different regions, and fulfilling various 
functions—e.g., mouths, swimming bells, grasping appendages, and 
reproductive bodies, attached or becoming separated, as free jelly 
fish ; all acting as members of one household. Professor Kélliker 
has lately made the discovery of true polymorphism among various 
genera of Anthozoa also. This polymorphism consists in the exist- 
ence, besides the large individuals capable of taking nourishment 
and furnished with generative organs, of other smaller, asexual 
individuals, which appear essentially to preside over the introduc- 
tion of sea-water into the organisms, and then over its expulsion, 
and which are, perhaps, at the same time, the seat of an excre- 
mentitial secretion. Like the others, these asexual individuals 
possess a body-cavity divided into chambers by eight septa, and a 
pyriform stomach with two orifices. On the other hand, they are 
entirely destitute of tentacles; and instead of the eight ordinary 
