TEST QUESTIONS FOR STUDENTS 919 



49. Give an illustrated account of the external characters of a typical 

 caterpillar. 



50. Make a tabulated survey of the chief types of larva among 

 insects. [(a) Campodeiform, and '' hard grubs " derivable from the 

 Campodeiforni type. (b) Eruciform — caterpillar, grub, maggot 

 (c) Peculiar types, such as the aquatic larvae of some Diptera.] 



51. In regard to Molluscs, explain the nature of the " foot," the 

 " mantle," and the " shell-sac." Contrast the shells of Nautilus, 

 Spirula, and the female Argonaut. Compare the black slug {Arion 

 ater) and the grey slug [Litnax) as regards shell. 



52. In the case of the crayfish, note in regard to respiration : (a) the 

 essential facts in the process, {b) the essential structures concerned and 

 their adaptations to their function, and (c) the auxiliary mechanism. 

 Do the same for fish, frog, bird, and mammal. 



53. Compare the aUmentary canal of a crayfish with that of a fish, to 

 bring out the fundamental differences. 



54. Why is moulting or ecdysis universal among Arthropods ? [The 

 external cuticle being a non-hving product cannot grow, nor is there 

 any free edge to which additions can be made to suit the continued 

 growth of the animal within.] 



55. Mention five different ways in which Arthropods solve the 

 problem of respiration, giving examples. [Gills (in higher Crustacea), 

 tracheae (in Insects, etc.), Lung-books (in Scorpion, etc.). Gill-books 

 (in King-crab), Cutaneous respiration (in some of the lower Crustacea).] 



56. How do the eyes of a lobster differ from ours ? [Skin-eyes not 

 brain-eyes ; compound, i.e. with many lenses and other parts, not 

 simple, i.e. with one lens ; forming an erect image not an inverted 

 image on the percipient surface ; stalked ; lidless ; and so on.] 



57. How does a crab deal with a badly damaged leg ? [At the 

 breaking joint near the base a forcible contraction of antagonistic 

 muscles detaches the damaged hmb ; a preformed, paired membrane 

 below the breaking plane folds over the wound preventing hsemorrbagc ; 

 under the shelter of this, in the basal stump a new limb is formed in 

 miniature ; this is set suddenly free at a subsequent moult and hardens 

 rapidly ; when exposed it is fully formed but not full-grown.] 



58. Explain what is meant by autotomy and give examples. [The 

 reflex breaking-off of an appendage or part of the body in the spasms of 

 capture or in other critical situations. There is extreme contraction of 

 muscles at a particular place, where there is often a structural pre- 

 arrangement. It is not to be thought of as deliberate, but as reflex. 

 It is usually followed by regeneration and is often a Ufe-saving adapta- 

 tion. The starfish surrenders an arm, the crab a leg, the lizard its tail.] 



59. How do a lobster's tendons differ from ours ? [Cuticular and 

 chitinoid, not composed of living connective tissue ; attaching the 

 muscles to the cuticle, not to bone ; periodically moulted, as long as 

 growing continues.] 



60. Why must a growing crayfish periodically get rid of its gastric 

 mill? 



61. Define a cuticle and give examples. [A non-cellular, non-living, 

 protective layer, usually external, made and remade by the underlying 

 living epidermis, or, it may be, by iuturned ectoderm. The armour of 



