826 TEST QUESTIONS FOR STUDENTS 



151. Make an illustrated comparison of the pectoral and pelvic 

 girdles in the following types, colouring homologous parts with the 

 same colour : frog, tortoise, lizard, crocodile, flying bird, running 

 bird, monotreme, rabbit. 



152. Explain what is meant by division of labour, and illustrate 

 your answer with reference to its occurrence among cells, among 

 regions of a particular organ, among organs, among members of a 

 physically continuous colony, among the discontinuous members of a 

 community. 



153. It is easy to get a burrowing Vertebrate, e.g., a burrowing 

 snake, superficially like an earthworm, and of the same size. How 

 would you distinguish the two tf convergent " types, and which differences 

 do you regard as most fundamental ? 



1 54. How are the young of the following animals nourished in their 

 early stages of development, and how do they breathe to begin with 

 skate or dogfish, frog, crocodile, fowl, duckmole, rabbit ? 



155. Make a comparison in detail between the vertebral column 

 in three Vertebrate types (such as frog, tortoise, pigeon, and whale), 

 and explain why the differences are so great. 



156. Explain what is meant by Natural Selection. 



157. Define parthenogenesis, give examples, and explain what is 

 meant by artificial parthenogenesis. [The development of an egg-cell 

 without being fertilised by a sperm-cell, as in many Rotifers, for long 

 periods among many water-fleas, in summer generations of Aphides, 

 in those queen-bee's eggs that develop into drones. In a variety of 

 cases, in which natural parthenogenesis is unknown, e.g. , starfish and 

 sea-urchin and up to the level of frogs, an egg may be induced by 

 various artificial methods to begin its development without being 

 fertilised by a spermatozoon. There are usually two steps : first, the 

 egg is activated by some stimulus, such as altering the chemical com- 

 position of the sea-water, or pricking the frog's eggs and bathing them 

 with blood ; second, the tendency to fatally rapid development and 

 dissolution of cells is checked by some counteractive, such as restoring 

 the egg to the normal medium,] 



158. Mention in order all the outgrowths from the alimentary canal 

 of Vertebrates. [Not including the oral part of the hypophysis, which 

 arises from the roof of the stomodseum, the list is as follows : gill- 

 pouches (which come to nothing above Amphibians, except that the 

 first forms the Eustachian tube), the thyroid, the swim-bladder (in 

 most fishes) or the lungs (above fishes), the liver, the pancreas, various 

 caeca, the allantois.] 



159. What are hormones? [Diffusible chemical substances, not 

 of the nature of ferments, produced by ductless glands or glandular 

 tissues (such as the thyroid gland, the supra-renal capsule, the pituitary 

 body, or the interstititial tissue of the testis, or the corpus luteum of 

 the ovary). These ductless, endocrinal, " internal -secretion " glands 

 have a rich vascular supply which carries away the hormones, which 

 activate or inhibit or control metabolic processes in various parts 

 of the body.] 



1 60. The development of the individual is in certain respects, 

 especially as regards organogenesis, a condensed recapitulation of the 



