^22 TEST QUESTIONS FOR STUDENTS 



lies and swims on its ventral surface ; the flounder is flattened laterall5% 

 and rests and swims on its left-hand side. The skate has placoid 

 scales, jelly-tubes, no gill-cover, gill-pouches separated from one 

 another, a conus arteriosus*, a spiral valve, internal fertihsation, and 

 so on. The flounder has " soft " scales, a lateral hne, a gill-cover, 

 gills fastened at each end only and not in separate pouches, a bulbus 

 arteriosus, no spiral valve, external fertilisation, and so on.] 



90. What is a mermaid's purse ? [The egg-case or egg-shell, and, 

 to begin with, the enclosed ovum or embryo of a gristly (Elasmobranch) 

 fish, such as skate or dogfish. The case is made of horn or keratin, 

 like om finger-nails ; it coalesces from fluent strands secreted by the 

 oviducal gland ; the tendrils may entangle on sea-weed, preventing 

 smothering : a chemical change emanating from the embryo dissolves 

 the purse at one end and allows of the escape of the young fish.] 



91. Make a statement in parallel columns of the essential differences 

 between a fish and a crayfish. [Vertebrate contrasted with Invertebrate.] 



92. How do Cyclostomes differ from Fishes proper? [Jawless, 

 limbless, scaleless, with unpaired nostril, with peculiar gill-purses, etc.] 



93. In what various ways is respiration effected in a frog in the 

 course of its life-history ? [Cutaneously, by three pairs of ectodermic 

 gills (first set), gill-clefts are added, by a second set of ectodermic gills, 

 by lungs and gills, by lungs and skin, by skin only in winter.] 



94. What noteworthy advances or acquisitions were made by 

 Amphibians ? [Fingers and toes, true ventral lungs, posterior nares, 

 a 3-chambered heart, an inferior vena cava (also in Dipnoi), a movable 

 tongue, a larynx with vocal cords, and so on.] 



95. What is the mode of respiration in a newly-hatched skate, a 

 newly-hatched tadpole, a tadpole of one month, a tadpole of two 

 months, a frog in its winter hiding-place, an unhatched crocodile, 

 and an unborn mammal ? 



96. A frog has its hip-girdle loosely attached to one sacral vertebra ; 

 a bird has its hip-girdle fused (by the ilia) to a large number of 

 vertebrse, which form the syn-sacrum. Explain why the ilio-sacral 

 connection should be so very different in these two types. 



97. Mention the skeletal peculiarities of a frog's hind-leg, explaining 

 precisely what the peculiarity is. 



98. How would you at once distinguish between a newt and a lizard ? 

 '99. Give three good examples of structural adaptations in Reptiles, 



explaining in each case how the adaptation works. [The deep ball- 

 and-socket centra of a snake's vertebra; and the double articular 

 processes, which allow of great mobility without risk of dislocation. 

 The elongated protrusible tongue, split hands and feet, and prehensile 

 tail of chamaeleons. The inferior processes of anterior vertebra?, 

 enamel-tipped, which protrude through the roof of the gullet in the 

 egg-eating snake, Dasypeltis, and break the shells.] 



100. What is a snake's slough ? [A casting or moulting of the dead 

 outermost layer of the epidermis, carrying with it an imprint of every 

 scale. It comes off in a piece, turned inside out from head to tail. 

 Obviously, it could not be a casting of skin or of scales.] 



10 1. Describe the composition of the carapace and plastron in a 

 tortoise. 



