REPRODUCTION AND HEREDITY '289 



gland opens directly into the spur the horns of deer, the antlers 

 of stags, manes of horses and lions, and tusks of boars. In 

 addition we find that the males are furnished with better or 

 even new sense-organs for seeking, and with other preparations 

 for seizing and holding the females. 



The male Leptodora, a little transparent fresh- water crus- 

 tacean, which I have mentioned several times, possess greatly 

 prolonged antennae. 



The males of numerous beetles, butterflies, etc., are 

 also often distinguished by their strongly developed and highly 

 differentiated antennae. In the male of the honey-bee almost the 

 entire head is occupied by the greatly enlarged, faceted eyes, 

 while the queen and the workers possess considerably smaller 

 eyes. This extraordinary development of the organs of sight is 

 absolutely necessary for male bees if they do not wish to lose 

 sight of the queen during the rapid nuptial flight. In some 

 male flies of the genus Cloe and Potamanthus there are found 

 special ' turban eyes ' which are absent in the females flies. 

 Finally, we have already seen that the faculty of producing light 

 is of great assistance among many animals in the finding of the 

 sexes. 



Among the instruments for seizing and holding the females 

 I need only mention the gripping-antennae of several of the lower 

 crustaceans, the swelling on the ' thumb ' of the male frog, and 

 the spurs of the Ornithorhynchus. 



Fertilization may either be external, daring which the germ- 

 cells are simply voided into the water, or internal, with preceding 

 copulation. The first form is widely found, particularly in the 

 jelly-fishes, echinoderms, numerous vermes, mussels, tunicates, 

 fishes, and, finally, many amphibians. Though it may sound im- 

 probable, interior fertilization can take place without preceding 

 copulation, while, on the other hand, in a few animals with 

 external fertilization there is also a kind of copulative act per- 

 formed. 



While generally the male semen is secreted as a fluid, in 

 some animals so-called sperinatophores or ' sperm-cartridges ' are 

 formed. These are delicate capsules of many shapes and often 

 highly complex construction, which contain a large number of 

 mature spermatozoa. During pairing time we may often notice 

 a very attractive spectacle in many of the tritons. The male has 

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