I70 NATURAL SCIENCE. Sept.. 



to carry about bits of sea-weed and shell and small pebbles. By this 

 means they very successfully conceal themselves from the naturalist 

 and no doubt from other enemies ; but the edible Hipponoe is, un- 

 fortunately for itself, less an adept at the practice than is the species of 

 Toxopneiistes. 



Nematodes in the Blood of Man, 



The English race, among the many interesting things which 

 they bring back from the tropics, occasionally unwillingly bring back 

 for the consideration of English medical men parasites of the tropics. 

 In the new issue of the Transactions of the Norfolk and Norwich 

 Field Naturalists' Society Mr. H. D. Geldard describes an interest- 

 ing case of Filaria sanguinis hominis in the blood of a patient who 

 resided many years in India. The specimens abounded in the blood 

 of this patient, and were that larval phase of Filaria bancrofti which is 

 called Filaria nocturna, as it appears in the blood of man only from 

 sunset to sunrise. These young embryos are taken from the blood 

 by the female mosquito, which also is a nocturnal animal. A few 

 days after its meal the mosquito retires to water to deposit her eggs, 

 after which she dies, and her dead body drops into the pond or 

 stream. Within her body the embryos which had got into the 

 alimentary canal from the blood of man have been rapidly maturing. 

 They issue from her dead body by means of a boring apparatus 

 developed at their anterior end. They swim freely through the 

 water, and apparently ultimately perish unless they are swallowed in 

 the water by man. If this happens they bore their way from 

 the stomach to the lymphatic vessels, where they become 

 sexually mature. Each female pours out a multitude of small 

 embryos, each within a delicate egg-shell. These find their way 

 into the blood-vessels and lie concealed, except at night, when the 

 mosquito is active, and so gives the opportunity for this cycle of 

 development to begin again. The consequences of their presence in 

 man may be trifling, but by choking the lymphatics they may cause 

 some most unpleasant and dangerous diseases. 



Hop-Disease in Kent. 



We learn from Professor J. Percival, of the South-Eastern Agricul- 

 tural College, Wye, Kent, that he is at present engaged investigating 

 the disease which causes hops to become what is known as " nettle- 

 headed." The disease is met with in many districts in the county, 

 and has rapidly increased during the last few years — in some cases, 

 leading to a complete destruction of considerable areas of hop 

 gardens. The early delicate varieties are most attacked, and 

 especially those which have been growing for a considerable time. It 

 is rarely until five years after planting that the disease is seen, and 

 usually not until a much later period. 



