240 PROGBESS OF MICROSCOPICAL SCIENCE. 



the structure of the Echinoderms and that of the Annuloids." Now 

 the young of certain Echinoderms have a form very similar to larval 

 worms. " On this chiefly Professor Huxley, misled by the names given 

 by J. Miiller to some of these larva?, has revived the old opinion 

 of Oken, and associated the Echinoderms with the Articulates ; but as 

 he based his opinion entirely upon the figures of Miiller, and not 

 upon original investigations, his conclusions, which have been adopted 

 by the majority of English naturalists, do not appear to Mr. Agassiz 

 as tenable. The hypothetical form to which Huxley reduces these 

 larvsB, to make his comparisons and to draw his inferences, is one 

 which has never been observed, and as far as we now know does not 

 exist." Mr. Agassiz's paper, with many beautiful figures, appears in 

 the ' Memoirs of the American Academy of Arts and Sciences.' 



The Structure of the Cornea. — This has been very well investigated 

 by Dr. Thin, who has communicated a paper on the subject, through 

 Professor Huxley, to the Royal Society. The paper appears in the 

 last number but one of the ' Proceedings of the Royal Society.' The 

 author says, referring to his former paper,* that in " order to 

 corroborate the results yielded me by the nitrate of silver, I 

 availed myself of the well-kno^\Ti property which haematoxylin pos- 

 sesses of specially staining the nuclei of cells. I allow the cornea 

 to remain in the solution until it is perfectly saturated. Subsequent 

 maceration in acetic acid removes the haematoxylin from the fibrillary 

 substance before it bleaches the nuclei. On comparing a cornea so 

 treated with successful preparations of the cornea-corpuscles as 

 obtained by chloride of gold, it is found that the number of cells 

 demonstrated by the haematoxylin exceeds by several times that found 

 in the gold preparation, affording direct proof of the existence of other 

 cells in the cornea than those known as the cornea-corpuscles. If a 

 vertical section of the cornea is so treated by hnematoxylin and acetic 

 acid, in many of the clefts of the fibrillary substance, in which, as is 

 well known, the cornea-corjiuscles are situated, several nuclei are seen, 

 proving in another way the existence of a greater number of cells than 

 those hitherto accepted by anatomists. But in addition to the proof 

 aftorded by staining the nuclei of the cells, I have, by the application 

 of a new method, been able to isolate (and thus demonstrate beyond 

 all further possibility of doubt their existence in the cornea) a large 

 number of cellular elements, the varied size and shape of which 

 distinguish them not only from the cornea-corpuscles, but from any 

 anatomical structures that have been as yet described. K a cornea is 

 placed in a saturated solution of caustic potash, at a temperature 

 between 105° and 115^ Fahrenheit, it is reduced in a few minutes to 

 a white granulated mass of about a fourth of its previous bulk. In a 

 small piece of the diminished cornea, broken down with a needle and 

 examined under the microscoi^e in the same fluid, it is found that the 

 only visible elements are a great number of cells. If the conjunctival 

 epithelium of the cornea has not been previously removed, the cells of 

 that structure can be recognized amongst the others ; and if the mass 

 under examination has not been too much broken up in maiiipiilatiug, 

 * ' Lancet,' February 14. 



