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BRITISH FOSSIL CRUSTACEA. 



two years, 1 he was supplied by Dr. Lockwood, in the Springs of 1870 and 1871, with, 

 numerous specimens of the freshly laid eggs of Limulus for examination, and he pays a 

 well-earned tribute to the ardour and enthusiasm of this excellent naturalist to whose 

 original observations we are greatly indebted for the present state of our knowledge of 

 the early stages in the life of this remarkable Crustacean. 



The freshly laid eggs of Limulus measure "07 of an inch in diameter, and are green in 

 colour. 



The annexed figures (Woodcuts, fig. 74 — 77) introduce us to some of the earliest 

 appearances presented by the ova observed under the microscope by Dr. A. S. Packard. 



Earliest stages in the Embryology of the Limulus polypkemus (after Packard). 2 



Fig. 74. 



Fig. 75. 



Fig. 76 



Fig. 74. Cell-egg, with 

 yolk-cells developing. 

 x 130 diams. a, the 

 nucleolus ; b, the nu- 

 cleus ; c, layer of pro- 

 toplasm surrounding 

 the nucleus (germ- 

 yolk) ; d, d, yolk-cells 

 developing. 



Fig. 75. — Portion of sur- 

 face of freshly impreg- 

 nated egg after the 

 primitive cells have 

 disappeared. x 30 

 diameters. 



Fig. 76. — Portion of egg 

 seen in section, ch, 

 chorion ; p, protoderm 

 or amnion, not yet 

 moulted; e, the blasto- 

 derm and yolk-cells, 

 x 130 diameters. 



Fig. 77. — Early stage of 

 embryo, pm, the am- 

 nion ; x, x, yolk-masses 

 detached before the 

 formation of the blas- 

 todermic skin. [See 

 also PI. XXXIII, fig. 1.] 



" We see in Fig. 74 the commencement of the formation in the cell-egg of a central 

 mass of larger and denser granules constituting the nucleus (3) within which is the hyaline 

 nucleolus {a). Round this is the mass of germ-yolk (c) in which are recognisable granules 

 round other centres or yolk-cells (a). 



After impregnation a denser aggregation of the blastodermic cells takes place on the 

 surface (Fig. 75, c). 



1 It is proper to mention here that Dr. Anton Dohrn, of Jena, first induced Dr. Packard to seek 

 for the eggs of Limulus on the American coast. The specimens examined by Dr. Anton Dohrn, and 

 ■which furnished the materials for his paper, were supplied to him by Dr. Packard. It is to be regretted 

 that, owing to the distance at which Dr. Dohrn's studies were carried on, he could only examine 

 specimens preserved in spirits, which prevented him from fully completing his researches. He has, 

 however, added some valuable materials towards the completion of our knowledge of the embryology of 

 Limulus, for which as well as for other valuable papers on the Arthropoda he deserves our best thanks. 



2 These four woodcuts, engraved for Prof. Owen's "Memoir," 'Trans. Linn. Soc.,' vol. xxviii, 1873, 

 part iii, p. 488, have, with the author's approval, been most kindly lent for this work by the Council of 

 the Linnean Society. 



