ZOOLO&y AND BOTANY, MICROSCOPY, ETC. 57 



limb are so different to those of the Phyllopod as to lead to the view 

 that the Decapoda have risen from the nauplius independently of the 

 Phyllopoda ; and it would appear that the entire leg of the Phyl- 

 lopod (without the gill and flabellum) is homologous with the endo- 

 podite of the Decapod maxilliped and the gill and flabellum with 

 those of the Decapoda. The appendages of Limulus may be brought 

 into relation with those of other Crustacea by appending an exopodite 

 to the coxopodite, and arranging the gills on the outer side of a more 

 or less cylindrical epipodite, instead of having them set antero-poste- 

 riorly. The author insists that radical changes of structure and 

 changes in function may be seen in the Malacostraca, and he argues 

 that still greater modifications may have obtained in the Palseocarides, 

 of which Limulus is the sole survivor. The resemblances to the 

 Arachnida are looked upon as merely analogous, and it is urged that 

 the synthetic characters of Limulus may be shown to be very striking 

 when a longitudinal section of it is compared with one of Apus ; there 

 may be seen such resemblances as the lobules of the liver filling the 

 front part of the head, the oblique, long, narrow oesophagus, the position 

 of the stomach under the eye, the simple archi-cerebrum, the general 

 form of the heart, and the " gnathobases " near the mouth. 



Characters of Nebalia.* — Dr. Packard also gives an account of 

 the structure of Nebalia, a form which is of particular interest from 

 "its composite nature," and its relation to some fossils which are 

 generally regarded as Phyllopods. After an examination of the 

 appendages the author points out that there is only a general homo- 

 logy between the thin, lamellar, thoracic foot of Nebalia and that of 

 any Decapod ; when the thoracic legs of the adult Nebalia are com- 

 pared with the maxillipedes of the zoea of the Decapods, a slight and 

 interesting resemblance may be detected, but not so close a homology 

 as between the maxill89 of the zoea and the thoracic legs of the 

 Phyllopods. In fine, the resemblances are so slight that we are forced 

 to confess that Nebalia is not a Decapod. The form is, further, 

 distinguished by the absence of a telson. 



During the history of its development the diagnostic ordinal 

 characters of the Phyllocarida declare themselves : the large movable 

 rostrum, the compressed pseudobivalvular carapace, the lack of 

 maxillipedes, the eight pseudophyllopod thoracic feet, and four pairs 

 of abdominal feet, out of the six of the adult. Mysis does not seem 

 to be descended from a Nebalioid, but from a zoea-form. The 

 Phyllocarida have had no Decapod blood in them, so to speak, but 

 have descended by a separate line from Copepod-like ancestors, and 

 culminated and even began to disappear before any Malacostraca, at 

 least in any numbers, appeared. 



Nervous System of Palaemonetes varians.f — A. Garbini describes 

 the different parts of the nervous system and the sense-organs. Of 

 especial interest are certain bodies found on the endopodites of the 



* Amer. Nat, xvi. (1882) pp. 861-73 (3 pis.). 



+ Atti Soc. Veneto-Trentina, vii. (1882) (6 pis.). Cf. Bull. Soc. Entomol. 

 Ital., xiv. (1882) p. 250. 



