818 TEST QUESTIONS FOR STUDENTS 



35. Explain how meiotic or reducing division differs from ordinary 

 mitotic or equation division. 



36. How does a starfish climb up a rock ? [(#) Making tube-feet 

 tense with water from water- vascular system, pressing them against 

 the rock, fixing them by a back-flow forming a partial vacuum at the 

 tip, drawing the body up by contracting the muscles of the tube-feet, 

 fixing another set of tube-feet and freeing the first set by the injection 

 of water forcibly from the muscular ampullae.] 



37. How does the " test " of a sea-urchin differ fundamentally from 

 the shell or skeleton of a cup-coral ? 



38. Compare the external features of a starfish and a sea-urchin, 

 indicating the parts that correspond. [The dorsal surface of the starfish 

 = the apical disc of the sea-urchin ; the ventral surface of the starfish 

 with the ambulacral groove and tube-feet = the ambulacral areas of the 

 sea-urchin ; the sides of the arms of the starfish = the inter-ambulacral 

 areas of the sea-urchin ; the madreporic plates correspond ; the mouth 

 and the anus occupy corresponding positions in the two types ; and 

 so on.] 



39. Give an illustrated account of the typical process of cell-division. 

 What is the advantage of so complicated a process ? 



40. What is meant by a " synthetic type ? " Illustrate with reference 

 to Peripatus. [A type which shows characteristic features of two very 

 different classes or groups. It may be regarded as a connecting-link or 

 as a collateral relative of a connecting-link between the two classes or 

 groups. Thus Peripatus is like Annelids in its musculature, simple 

 limbs, "nephridia, etc., and like Tracheates in having limbs in the 

 service of the mouth, antennae, tracheae, etc.] 



41. State briefly what takes place inside the pupa-case of an insect. 

 [A continuation of processes of disintegregation or histolysis of larval 

 organs, and of processes of reconstruction or histogenesis on a new 

 architectural plan that of the adult or imago. In the reconstruction 

 an important part is played by clusters of formative cells which grow 

 inwards from the body-wall and serve as foci of new development. 

 They are called imaginal folds or discs.] 



42. Why has a drone-bee no sting ? 



43. Why do not aquatic insects drown ? 



44. Why is a tapeworm not digested in the intestine of its host ? 



45. Give a working definition of instinctive behaviour. [A routine 

 chain of effective actions, performed more or less independently of 

 learning, in virtue of an inborn prearrangement of nerve-cells and 

 muscle-cells (forming reflex arcs), but suffused with awareness, and 

 backed by endeavour, e.g. , a young bee visiting a flower ; a young 

 spider spinning its web.] 



46. What is the morphological nature of (a) a bee's sting, (b) a 

 spider's spinnerets, (c) a locust's ovipositor, (d) a scorpion's " pectines." 

 [Transformed abdominal appendages.] 



47. Explain carefully how you would distinguish between a spider 

 and an insect, even if the insect were wingless. 



48. Give an illustrated account of the life-history of the common 

 house-fly, Musca domestica^ and indicate briefly how its habits render 

 it dangerous to man. 



