344 NATURAL SCIENCE. May. 



separate operations, it is because a portion of a last year's float has 

 remained. 



Of the larvae, those of Lamellariida:: were characterised by the 

 possession of a broad, hyaline " scaphoconch." One of the com- 

 monest was that known as Echinospira, which is probably the young 

 oi Laviellavia pevspicna. The remaining larvae are classed in seventeen 

 categories, among which only a few can be mentioned here. 

 Macgillivrayia, the larva of Dolmm, is widely distributed ; it has long 

 bristles, and the operculum has a vertical median ridge on the inner 

 surface for the attachment of the columellar-muscle, besides which a 

 system of comma-like dots oblique to the ridge indicates incipient 

 torsion. In Simtsigera, a collective name for the larvae of Mtirex, 

 Purpura, Bela, Triforis, Cyprcra, etc., the notch is correlated with the 

 protrusion of a sail-like lobe of the velum. In this group the 

 metamorphosis of the shell is very distinct : the larval shell (prosopo- 

 conch) is often clearly distinguishable at the apex of the definitive 

 shell (teleoconch), and usually bears at its own apex the original 

 embryonic shell (embryonoconch). One specimen suggested the 

 incipient shell of a Spirula, but, being smaller than would have been 

 expected, was probably referable to a species of Ccemm. 



Notwithstanding the difficulties of the enquiry, and the uncer- 

 tainty of the specific determinations, a few general principles may be 

 enunciated. Slender shells, the length-breadth ratio of which exceeds 

 5 : 2 occur only on the coasts, not in the plankton. All the larvae are 

 provided with enormous velar processes, with a complicated double 

 series of cilia, and a strong longitudinal retractor muscle. They have 

 a lacunar structure correlated with respiration. The sole of the foot, 

 though distensible, is extremely small, and the proboscis is wanting, 

 though its sheath occurs as a large pigmented sac. The radula could 

 not be used for systematic purposes, as its lateral and marginal teeth 

 showed different relations from those obtaining in the adult. With 

 respect to the shell, the embryonoconch is of structureless conchiolin. 

 The most primitive complication is the hair, resulting from some active 

 secretion on the mantle-margin ; longitudinal and transverse knobs 

 and prominences arise also in consequence of irregular secretion, and 

 in their simplest arrangement are compared with the staves and hoops 

 of a barrel : sometimes their deposition takes place at an angle of 

 45° to the axis. The colour of the shells is either yellow-orange or 

 blue-violet — that is to say, in the main, of one of two complementary 

 tints. The blue series is the result of exposure to the tropical sun ; only 

 forms which dive are colourless, and only swimming forms are 

 phosphorescent. 



It will be obvious, even from this brief outline, that the Memoir 

 contains many interesting and valuable facts and much suggestive 

 comment. It is beautifully illustrated, and we congratulate Dr. Simroth 

 on his courage in undertaking such a task and on the success which 

 he has achieved in discharging it. W. E. H. 



ECHINODERM EMBRYOLOGY. 

 Text-Book of the Embryology of Invertebrates. By E. Korschelt and 

 K. Heider; translated by E. L. Mark and W. McM. Woodworlh. Part I. 

 8vo. Pp. xvi., 484. London : Sonnenschein, 1895. Price 15s. 



The science of animal embryology advances so rapidly that English 

 students have anxiously awaited this long-promised translation of the 

 leading German manual. Delay has not, however, had the result of 

 rendering the book out-of-date. On the contrary, it is a considerable 

 improvement on the German edition, owing to the insertion of 



