ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 413 



There is an interesting chapter on anatomy. The author is more 

 strongly than ever of opinion that the so-called stigmata are sense- 

 organs. Some additions are made to the account of the mouth-organs. 

 Coition probably takes place by a bursa copulatrix within the anal 

 plates and in immediate proximity to the anus, and not at the vulva of 

 parturition within the genital plates. Mr. Michael finds that there is 

 not in every species a complete breaking-up or dissolution of all the 

 organs of the nymph prior to the formation of the adult ; in some cases, 

 at all events, some of the internal organs of the nymph are transferred 

 to the adult, and are not dissolved, but are identical in both stages. 

 Where dissolution and reformation have occurred in the specimens ob- 

 served by the author, the two processes have gone on simultaneously, 

 and there has not been any time when the cuticle contained only plastic 

 or liquid matter without any organs. In the earlier stages of this change 

 the contents of the nymphal skin have, in such cases as were observed, 

 shrunk backward towards the posterior portion of the creature, leaving 

 the cuticle of the rostrum, &c, empty, while the contents of the legs 

 have been withdrawn or shrunk inward into the body-substance, leaving 

 the cuticle of the legs empty. In the later stages of formation the 

 organs of the adult have again advanced forward nearer to the rostrum 

 of the nymphal cuticle, but not as far forward as the old organs originally 

 were. 



A list is given of foreign species of Oribatidse, and the work con- 

 cludes with a bibliography. There is a copious index. 



e. Crustacea. 



Palpiform Organs of Crustacea.* — Prof. F. Plateau continues and 

 concludes his series of studies on the function of palps in Arthropods 

 by an investigation of the palpiform organs in Crustaceans. In an 

 introductory discussion of the homologies between the appendages of 

 Crustaceans and those of other Arthropods, he concludes (1) that neither 

 the pseudopalp of the mandible nor the so-called palps (exopodites) of 

 the three pairs of maxillipedes are homologues of the palps of insects, 

 and (2) that the real homologues are to be found in the endopodites of 

 the two pairs of maxillae and of the three pairs of maxillipedes. 



He then gives an account of his observations and experiments on 

 the following forms in order: — Talitrus saltator Montagu, Gam marus 

 pulex Linn., Porcellio scaber Latr., Oniscus mnrarius Cuv., Ligia oceanica 

 Linn., Asellus aquaticus Linn., Carcinus moenas Baster. 



His results on crabs disprove, he believes, (1) the opinion of Brulle, 

 Milne-Edwards, and Claus, that the maxillipedes of Crustaceans are 

 used in seizing food, and in conveying it between the other buccal 

 parts. This is quite erroneous as regards the Brachyura. The external 

 maxillipedes are merely auxiliary in retaining the food seized by the 

 claws and under the action of the mandibles. (2) The hypothesis of 

 Milne-Edwards and Huxley that the external, and probably also the 

 other pairs of maxillipedes, as w r ell as the maxillae proper, are of use in 

 mastication, is not true of crabs. There the mandibles alone are masti- 

 catory. (3) The function suggested by Duges and Rolleston that tho 

 mandibular palp is used to direct the food, is not supported by any 

 observed facts. In crabs it can be readily observed to have no such role. 



* Bull. Soc. Zool. France, xii. (1888) pp. 537-52 (11 figs.). 



