Royal Society. 297 



Fig. 2. Ileail of a somewhat smaller animal, from above : a, pharjux ; 



b, muscles ; c, brain ; d, " respiratory tubes." 



Fig. 3. Male Hydatina (Enteroji/ea Hijdutina) : a, the rudimentary intes- 

 tinal canal, to which the dark aggregations of granules, b, belong ; 



c, testis. 



Fig. 4. The hinder extremity of an Enteroplea, exactly in a lateral posi- 

 tion : a, remains of the tractus ; b, the aggregations of granules 

 (" uric concretions") ; c, testis ; (/, efferent ducts ; e, " prostate." 



Fig. 5. Spermatozoa of Enteroplea : fl, stiff, bacillar form; b, form fur- 

 nished with an undulating membrane. 



Fig. 6. The animal living in the stomach of the female Hydatina. It is 

 » represented in its various stages of contraction. 



PROCEEDINGS OF LEARxNED SOCIETIES. 



ROYAL SOCIETY. 



June 18, 1857. — The Lord Wrottesley, President, in the Chair. 



"On the Development of Carcinus Mcenas." By Spence Bate, 

 Esq., F.L.S. 



The author, after noticing the history of the subject, and the 

 opposition which the assertion, " that the Zoea of naturahsts is the 

 hirva of a common crab," received, traces the progress of the deve- 

 lopment of the animal from the Zoea to the adult, and endeavours to 

 demonstrate, that from the youngest to the most perfect form, the 

 changes are the result of no sudden transformation, but produced 

 by a gradual series of alterations contemporary with every succeeding 

 moult ; tliat the Zoea is connected with the Meyalopa, and the 

 latter with the adult by many intermediate gradations, each in itself 

 scarcely appreciable, and progressively approximating more and 

 more nearly to the more perfect stages. 



The author asserts that the development is earliest and most com- 

 plete anteriorly ; that when first born, the seventh or posterior segment 

 of the head, one or more of the posterior segments of the pereion 

 (thorax), and the penultimate of the pleon (abdomen) are wanting 

 iir the brachyurous Decapods ; but that this general law loses some- 

 what of its force in the descending scale of development ; and as it 

 becomes less persistent, the animal approximates in the larval con- 

 dition nearer to the form of the adult type ; while on the other 

 hand, the same appears to be a constant law of the depreciation in 

 adult forms, as exhibited in the more or less aberrant Amphipoda, 

 such as Cyrtophium, DuUchia, ike. The author likewise shows that 

 the appendages, which act the principal parts in the larvae, become 

 the secondary parts of the same organs in the perfect animal. For 

 instance, the lower antenna is represented in the larva by the com- 

 plementary appendage of the adult form ; the true antenna is de- 

 veloped from the base of the embryonic organ, which represents 



