252 PROGRESS OF MICROSCOPICAL SCIENCE. ["rumJi.Marriilo?' 



observations on the young stages of Echini made upon the collections 

 of Count Pourtales. With these Mr, Agassiz has been able to stufly 

 the young of thirty odd different species belonging to as many dif- 

 ferent genera. These observations are important and interesting. 

 Among other points of interest, the author states that the changes 

 some species undergo are so great that nothing would have been more 

 natural than to place the two extremes of the series not only in dif- 

 ferent species, but often in different genera, and even in different fami- 

 lies. The different stages of growth of Toxopneustes drohacMensis Ag., 

 represent in the younger stages Cidaris, then Hemicidaris, then Pseu- 

 dodiadema, Echinocidaris, and Heliocidaris. In Cidaris, Diadema, 

 and Garelia, the changes are less marked, and in Echinometra they 

 are greater than in any other genus of the regular Echini, " We fre- 

 quently find," says the author, " specimens of the same size, where in 

 one case the outline is almost circular, the test flattened, covered with 

 long slender spines ; while in the other the test is lobed, swollen, high, 

 siirmoimted by numerous short stout spines. Among the Clypeas- 

 troids we find in the young diu-ing their growth great changes of form 

 and structure taking place," The transformations of Mell'da testudi- 

 nata and Encope emarginata are described as identical, whilst those of 

 Mellita testudinata and Mellita hexapora are not so much alike, although 

 both of the same genus, " The development of Stolonoch/pus prostratus, 

 and flat Clypeastroids of the type of Clypeaster placunarius is most 

 instructive, tending to show that in connection with the develojjment 

 of the Scutellidse, we must probably introduce a complete reform 

 among the genera recognized as Lemtia, Scutellina, Euna, Echino- 

 cyamus, and other minute Echinoids, which may eventually prove 

 to be nothing but the young of other Cly2)eastroids, as Mellita, 

 Scutella, Laganum, Stolonoclypus, Clypeaster, Encope, and the like ; 

 but want of sufficient material prevents me from entering into this 

 comparison more in detail. Though we know now, from what has 

 been said above, that the Scutellidas pass through phases which cannot 

 be distinguished from Moulinsia Fibularia, Runa, Scutellina, and the 

 Clypeastroids proper pass, through a stage of growth identical with 

 Echinocyamus, The development of Echinolampas has thrown unex- 

 pected light upon the affinities of the toothless Galerites and of the 

 Cassidulidae, It shows conclusively that Echinoneus is only a per- 

 manent embryonic stage of EchinolamjDas, thus becoming allied to the 

 Cassidulida?, and that it has nothing in common with the Galerites 

 as I would limit them, confining them entirely to the group j)rovided 

 with teeth," 



Structure of Fossil Fern-stems. — Mr, Carruthers, who continues his 

 laborious researches on the subject of fossil plant-structure, recently 

 read a paper before the Geological Society, " On the Structiu-e of a Fern- 

 stem from the Lower Eocene of Heme Bay," and showed the great 

 value of the microscope in inquiries of that sort. He stated that the 

 structure of the plant in question most closely agreed with the living 

 Osmunda regalis, and certainly belonged to the Osmundaceae. The 

 broken petioles show a single crescentic vascular bundle. The section 

 of the true stem shows a white parenchymatous medulla, a narrow 



