LITERATURE. 319 



Mysidae and the Cumacea to the Arthrostraca, wliicli we must regard as derived 

 from the Schizopoda hy the degeneration of the dorsal sliield, the stalked eyes, 

 and the exopodites of the thoracic limbs. This derivation has recently been 

 strongly advocated by Boas (No. 4). It is supported by the structure of the 

 Anisopoda, in which rudimentary exopodites are retained on the two anterior 

 thoracic limbs, and by the presence of a remnant of the dorsal shield. It 

 receives further countenance from Nusbaum's observation in the emlnyo of 

 Ligia (Lit., p. 189, No. 85a) of a biramose rudiment in the case of all the 

 thoracic limbs. The Anisopoda are nearly related to the Isopoda, among which 

 Jsdlus especially has retained a primitive condition, while the Amphipoda 

 must be regarded as a more specialised group.* 



LITERATURE OF THE METAMORPHOSIS OF THE 



CRUSTACEA. 

 Crustacea in General. 



1. Bate, C. Spence. Eeport on the present state of our know- 



ledge of the Crustacea. Ilejwrt of the Dritidt Association 

 Adv. Set. 1878. 



2. Bate, C. Spexce, and Westwood, J. 0. A History of the 



British Sessile-eyed Crustacea. 2 Vols. London, 1861-1868. 



3. Bell, Th. A History of the British Stalk- eyed Crustacea. 



London, 1853. 



4. Boas, J. E. Y. Studien liber die Verwandtschaftsbeziehungen 



der Malacostraken. IlorpJi. Jahrb. Bd. viii. 1883. 



5. Claus, C. Die morphologiscben Beziehungen der Copepoden, 



Pliyllopoden, Cirrhipedien etc. Zeitscbr. Xatiirwiss. Wiirz- 

 bur£?. Bd. iii. 1862. 



"^tr 



* [Anaspidcs, a most remarkable fresh -water Crustacean from Tasmania, 

 combines in many res})ects the characters of the Schizopoda and Arthrostraca. 

 In general form it resembles the Amjihijtoda, but it possesses stalk eyes, 

 auditory organs in the two-jointed ]iroto})oiiite of the antennule, exojiodites 

 and epipodial plates on the thoracic limbs, and typical biramose swimmerets 

 on the abdomen. It was placed bj^ Thomson {Trans. Lin. Soc. Zool. (2), vi. 3) 

 among the Schizojtoda. Great interest lies in the comparison made by Calman 

 ( Trans. Ron. Soc. Edinb., xxxviii., p. 787) between Anaspides and the Palaeozoic 

 forms Palaeocaris, Gainpsony.r, and Acanthotelson. — Ed.] 



[Since the above was published in 1891, a new attemjit has been made to 

 deduce the Crustacea from the Phyllopoda, Apus being the form which, it is 

 claimed, supplies all the requirements of tlie common ancestor. Bernard's 

 arguments are too numerous to be detailed here, and slioidd be studied in the 

 originals (App. to Lit. on Crust, in Gen., I. and II.). AVe will confine ourselves 

 to remarking that this derivation would account for the ver}^ general presence 

 of the NuKplius larval form, the Nanplius Ijeing merely the young Apus stage 

 in the development of its derived forms. Bernaud's method of deducing Apus 

 from an Annelid with its prostoniium and moutli bent ventrally so as to use its 

 parapodia as jaws seems, as he claims, to find suppoi't from the varying mouth- 

 jiarts of the Trilobita and the Gigantostraca, and, in general, it must be admitted 

 that the recent discoveries of the a]ipendages of Trilobites liave largely heljied to 

 confirm his argument. On the other liand, it has led him to conclusions about 

 the origin of the sliell- and antennal-glands, whicli most investigators of the 

 ontogeny of these organs will not regard as justifiable. — Ed.] 



