Mr. Needham from this conceives that we might imagine the actions of all this machine were owing to the spring of the screw, but he proves, by many experiments, that the screw, on the contrary, only obeys a power which resides in the spongy part. As soon as the screw is separated from the rest, it ceases its action, and loses all its activity. The author afterwards makes this reflection on this singular machine: "If, says he, I had seen the animalcule pretended to be in the semen of living animals, perhaps I might be in a condition to determine whether they are really living creatures, or simple machines prodigiously minute, and which are in miniature, what the vessels of the calmar are in the great." By this, and some other analogies, Mr. Needham concludes, there is a great appearance that the spermatic worms of other animals are only organized bodies and machines, like to those of the calmar, whose actions are made at different times; "for, says he, let us suppose, that in the prodigious number of spermatic worms seen on the table of a microscope, there are some thousands which act at the same time, that will be sufficient to shew us, they are all alive. Let us also conceive, adds he, that the motion of these spermatic worms remains, like that of the machines of the calmar, about half a minute; then the succession of action of these small machines, will remain a long time, and the pretended animals will appear to decrease successively. Besides why should the calmar alone have machines in its seed, whereas every other animal has spermatic worms, and real animals? Analogy is here of such great weight, that it does not appear possible to refuse it." Mr. Needham likewise very justly remarks, that even the observations of Leeuwenhoek, seems to indicate that the spermatic worms have a great resemblance with the organized bodies in the seed of the calmar. "I have, says Leeuwenhoek, speaking of the cod, taken those real substances for hollow and extended animalcule, because they were four times as large as the living animalcule." And in another part, "I have remarked, he says, speaking of the seed of a dog, that the animalcules often change their form, especially when the liquor in which they float evaporates. The progressive motion does not extend above the diameter of a hair."[R] [R] See Leeuwenh. Arch. Nat. page 306, 309, 310.