222 Notes, iv. 5. 



21. Cf. iii. 2, Notes 7 and 8 ; iii. 14, Note 32. 



.22. Cf. iv. 8, Note I. ' • . 



23. Cf.NoteS. 



24. The oesophagus in Crastacea is, as stated in the text, very short. The stomach- 

 teeth are present in all Decapoda, and not only "in the Carabi and some of the crabs."- 

 The intestine is remarkably straight. 



25. A.'s Ostracodernia,- or Testacea, ificlude all such bloodless* animals as have their 

 soft parts within, and their hard part without ; the hard part being brittle, and not 

 flexible as in Crustacea {H. A. iv. I, 4). Of their internal structure A. had made out 

 little or nothing. He divides the group, as do modern naturalists, by the character of 

 the. shell. . • 



I. Those witR a single spiral shell, the-Turbinata. 

 • 2. Those with a single non-spiral shell, or the Univalves, e.g. limpets. 

 . 3. Those with a double shell, the Bivalves; which are again subdivided into those 

 whose valves can open, as the mussels, and those wjiose valves -are always 

 closed, as the razor-fishes. '. 



4. Those that are completely enclosed in a* hard globular shell, i.e. the Echini. » 

 , 5. Those that are completely enclosed in a shell, of the consistency of leather, i.e. 

 the Ascidians (cf. Note 35). , To this group, though included amon^ Testacea, 

 the general definition of the Testacea, that they have a brittle and not a flexible 

 shell, is inapplicable. . • 



26. Bronn {Malacozoa, part ii. 950), and Lebert {Miiiler's Archiv. 1846, p. 463), 

 believe that A. means the lingual teeth. But these are almost too small to be seen with • 

 the naked eye. So Lebert boldly asserts that A. must have used a lens of glass or 

 crystal, or some magnifying instrument ! Clearly, however, the jaws are meant, not 

 the lingual teeth : for they are said to be only two in num"ber. Cf. Note 10. 



27. In many ■ gasteropods, e.g. the whelk, there is a long retractile proboscis. 

 Aristotle gives a much fuller account of the anatomy of the Mollusca in the H. A. i\. 4. 

 Neither there nor here, however, is it possible to identify with certainty the various 

 organs which he describes ; because there are considerable differences betw^een different 

 species ; and we do not know which species was taken by A. as the basis of his account. 

 Probably, however, he had examined the whelk, as he so frequently mentions it. 



281 The crop, wrhich comes directly after the mouth, is probably the " buccal mass " ; 

 for the dilatation which we call crop in many gasteropods {e.g. Dolium, Cypraea, 

 Voluta) is as a rule removed from the mouth by half the length of the oesophagus, 

 though exceptionally (e.g. Turbo) it may be much nearer, Cf. Bronn, Malacozoa, 

 part ii. 954. • 



29. The mecon (cf. Note 13) is the liver, which in all Gasteropoda is of great size, 

 and fills a large portion of the visceral cavity. It is of a dark brown colour, as also 

 is poppy-juice ; which fact is supposed to explain its name ; mecon being the Greek 

 word for that juice. Meconium is still the name given to the bile accumulated in the 

 intestine of the new-bom child. • 



The stomach is here said to . contain the mecon, and the gut to siart not from the 

 stomach, but from this latter. A. seems to have taken the thin membrane which encloses 

 the visceral mass for the stomach. Inside this membrane is the liver, hiding the true 

 stomach, and appearing to give origin to the gut which issues from it. 



30. Cf. ii. 17, Note 15. • . 



31. That all Turbinata have opercula is of course an error. In mahy genera, especially 

 those with larger apertures, it is quite' rudimentary or obsolete ( Woodward^ s Manual, 



