78 PROGRESS OF MICROSCOPICAL SCIENCE. 



tions, and it is not impossible that both heat and pollen may have to 

 do with the development of hay-fever. He says in the conclusion of 

 his fourth chapter, p. 153, that " 1 have shown that pollen of all kinds 

 will give rise to some of the symptoms of hay-fever, and that all the 

 other so called causes have little or nothing to do with generating the 

 disease. I have also shown that the actual attacks of the disorder as 

 they occur in the summer, are caused by the pollen which floats in the 

 atmosphere at this time." Then he goes on to say that in the atmo- 

 sphere at a certain height there is a zone which contains a greater 

 amount of germs and spores than are found at any other height, and 

 he inquii'es how far this has to do with the spread of disease. But 

 such questions of course cannot be answered definitely. Indeed, it 

 seems likely that such a distinct stratum in the atmosphere has no 

 existence whatever. It seems to us that the author has failed in one 

 portion of his study. He has done all parts of the microscopic work 

 creditably, as far as regards the inquiry as to the amount of pollen in 

 the air ; but he has not sufficiently examined the matter extracted from 

 the lungs and eyes of sufferers from this disease, to observe beyond 

 question that pollen grains were present in all cases. Still, it must 

 not be sujiposed that we think his views undeserving of consideration, 

 for they are well matured and elaborately laid down ; on the con- 

 trary, we think most highly of them, and we have pleasure in com- 

 mending his book to our readers' attention. 



PEOGEESS OF MICEOSCOPICAL SCIENCE. 



Milne Edwards on the Circulation in Limulus. — According to late 

 investigations which he has made on this subject, it would seem that 

 the circulating apparatus of Limulus is more perfect and complicated 

 than that of any other articulate animal. The venous blood, instead 

 of being diffused through interorganic lacunae, as in the Crustacea, is, 

 for a considerable portion of its course, enclosed in proper vessels 

 with walls perfectly distinct from the adjacent organs, originating 

 frequently by ramifications of remarkable delicacy, and opening into 

 reservoirs which are for the most part well circumscribed. The 

 nutritive liquid passes from these reservoirs into the branchiae, and, 

 after having traversed these respiratory organs, arrives by a system of 

 branchio-cardiac canals, in a pericardiac chamber, then penetrates into 

 the heart, of which the dimensions are very considerable. It is then 

 driven into tubular arteries with resistant walls, the arrangement of 

 which is exceedingly complex, with frequent anastomoses, and of which 

 the terminal ramifications are of marvellous tenuity and abundance. 



The Brachio])od in Embryo is the subject of a paper read before the 

 late meeting of the American Association by Professor Morse. "We 

 may say of it that the embryo commences life as a little worm of four 

 segments, and after enjoying itself in swimming freely in the water 

 for awhile, attaches itself to the sea bottom by its posterior segment, 



