THE frequency with which the successive numbers of the Quarterly Journal of Microscopical Science make their appearance may be taken as an index of the activity in research—of a particular kind—on the part of British biologists, and the editor is to be congratulated on the issue of seven parts of what used to be literally a quarterly journal during the last twelve months. The April number (vol. lv., part i.) maintains the usual high standard of this publication. It opens with a detailed description, by Prof. G. C. Bourne, of the anatomy of a remarkable New Zealand mollusc, Incisura (Scissurella) lytteltonensis, illustrated by five carefully drawn plates. Mr. W. J. Dakin gives a very full description and discussion of the eye of the scallop—Pecten—an organ which, on account of a certain resemblance to the vertebrate type of eye, has for a long time past attracted a large share of attention from biologists, and which lately, we believe, has played a not unimportant part in the theories of philosophers. Mr. Dakin concludes that “there is no ground whatever for placing the Pecten eye in the same class as the vertebrate eye, for the resemblance is very superficial, and though the retina is inverted in both cases, this has been produced in very different ways.” Prof. E. A. Minchin and Dr. H. M. Woodcock have a paper on the blood-parasites of certain fishes, accompanied by three of those remarkably beautiful plates which we have learnt to expect from proto-zoologists. A special welcome should be extended to another protozoological paper, the first, we believe, from the pen of Mr. Julian S. Huxley, grandson of Prof. T. H. Huxley, which deals in a very thorough manner with a new genus and species of gregarine from the digestive tract of that remarkable crustacean Anaspides tasmaniae. Both this memoir and that by Prof. Bourne, already referred to, are based on material obtained by Mr. Geoffrey Smith on his recent trip to Australasia. The number concludes with a reprint of Prof. Hubrecht's address to the Boston meeting of the International Zoological Congress on the fcetal membranes of the vertebrates, in which the author elaborates his remarkable views on the interpretation of mammalian development.