ADDITIONS AND CORRECTIONS. xvii 



p. 483. On the asymmetry of Gastropoda^ Biitschli, M. J. xii. 1887. 

 p. 509. Add the following definitions of Thysanura and Collembola : 



1. Thysanura. Rings of the thorax similar; abdomen with ten somites, 

 elongate, terminated by 2-3 appendages usually jointed; rudimentary abdominal 

 limbs sometimes present ; antennae long, many jointed ; maxillary palpi y-jointed, 

 labial 4-jointed ; e. g. Campodea, Lepisma, Machilis. 



2. Collembola. Prothorax small, meso- and meta-thorax not clearly segmented, 

 or the pro- concealed by the meso-thorax; abdomen with six somites, very often 

 globular, with a ventral adhesive tube and a terminal forked springing organ; 

 antennae 4-8 jointed, palpi absent ; e. g. Smynthurus, Podura. 



p. 519. Peripatus Capensis. Sedgwick has shown (Q. J. M. xxvii. 1887) that 

 the coelomic cavities of the somites persist as small vesicles in the appendages, that 

 the nephridia are the developed tubular portions of these cavities which obtain 

 external openings, and that the nephridia of the 3rd somite give origin to the salivary 

 glands. The coelome, so-called, of the adult, is a system of vascular spaces (=meta- 

 coele, p. xxix, post) developed independently of the cavities of the somites. The 

 generative cells are derived from the endoderm in the 6th-2oth somites, pass into 

 the dorsal parts of the true coelomic cavities of the same somites, which unite to 

 form the generative glands ; the generative ducts are developed from the coelomic 

 cavities of the 2ist somite; their openings are therefore nephridial. There are no 

 cilia in this species. 



p. 526. The Malpighian tubes of spiders (Araneidae) have been shown to 

 be, as in some Amphipoda, appended to the mesenteron, not to the proctodaeum ; 

 see Loman, Tijdschrift der Nederl. Dierk. Vereen. (2), i. p. 109. 



p. 562. Hamann, Beitrage zur Histologie der Echinodermen, pt. 3, Anat, 

 etc., der Echiniden und Spatangiden, Jena, 1887. Dorocidaris^ etc., Prouho, A. Z. 

 Expt. (2), v. 1887. 



p. 576. Mdmoire sur 1'Organisation, &c., Antedon rosacea, Perrier, Nouvelles 

 Archives du Musee, Paris (2), ix. 1886. 



p. 578. Catalogue of Blastoidea, Geol. Department Brit. Mus., Etheridge and 

 Carpenter, 1886. 



p. 588. For Echinoderes=Kinorhyncha, see Reinhard, Z. W. Z. xlv. 1887. 



p. 612. Nephridia etc. of Pofychaeta, J. T. Cunningham, Q. J. M. xxviii. (2), 

 1887. 



pp. 621, 622. The so-called sexual organs of Priapulidae, are both nephridial 

 and sexual, the two parts opening on opposite sides into the main canal. The 

 sexual part is developed last. Schauinsland, Z. A. ix. p. 574. 



p. 694. Sollas has shown that the coecal processes of the shell in Waldheimia 

 cranium lodge a sensory cell beneath the periostracum, which is connected by a fibril 

 to a nerve-ganglion cell in the mantle. Sc. Proc. Roy. Dublin Soc. v. 1886, p. 318. 



p. 711. Cephalodiscus proves to be an Enteropneustan, a near ally of 

 Balanoglossus. The epistome or buccal-shield is the proboscis, and contains 

 a coelomic cavity opening by two dorsal pores. It is followed by a collar with a 

 right and left coelomic cavity, opening each by a pore, and extending into the six 

 arms of each side. The body has also a right and left coelomic cavity. The nervous 

 system is ectodermal, and principally massed on the dorsal aspect of the collar, but 

 extends on to the proboscis and the arms. There is a pair of gill-slits overhung by an 



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