62 THE EVOLUTION OF SEX. 



fish, to serve this purpose, and the same is the case with minute 

 structures on the posterior abdomen of many insects. Some- 

 times, as in the snail (^Helix), which may be taken as an extreme 

 type of reproductive speciahsation, separate organs are present, 

 in which the spermatozoa are compacted into masses or packets, 

 known as spermatophores. In most cuttle-fishes, these pass 

 from the male ducts to one of the " arms," which thus laden is 

 occasionally set free bodily into the mantle-cavity of the female, 

 where it was of old mistaken for a worm, and called Hedocotylus. 

 So in some spiders, the palps near the mouth receive the male 

 elements, and transfer them to the female. Special storing 

 receptacles and secreting glands are also very frequently in 

 association with the male ducts, and there is a long list of 

 curious modifications utilised in the process of copulation. 

 Thus, male frogs have their swollen thumbs, and gristly fishes 

 their "claspers," which are modified parts of the hind limbs, 

 and are inserted into the cloaca of the female. The common 

 snails eject a limy dart {spiciilum amoris\ which appears to be 

 a preliminary excitant to copulation. 



So too, in the female sex, the terminations of the duct may 

 be modified for reception of the male intromittent organ, and 

 special receptacles may be present for storing the spermatozoa. 

 Where a single fertilisation occurs, as in the queen bee, previous 

 to a long-continued egg-laying period, the importance of a 

 storing organ is obvious. As the female is usually more or less 

 passive during copulation, the adaptations for this purpose are 

 less numerous than in the males. It is interesting to notice, 

 that among amphibians, where the male often takes upon him- 

 self distinctly maternal duties, one case is known where the 

 female seems more active than the male during copulation. 



§ 5. Egg-Laying Organs. — Cases where the ova simply pass 

 out into the water, or on to the land, are of course associated 

 with the absence of any special organs. In a great many 

 animals, however, more care is taken, and auxiliary structures 

 are present One of the simplest of useful developments is 

 exhibited by glands, the viscid secretion of which moors the 

 ova, and keeps them from being set wholly adrift. In insects, 

 where it is specially important that the eggs should be well con- 

 cealed, or buried in conveniently nutritive material, hints of 

 the ancestral abdominal appendages remain as "ovipositors." 

 Throughout the series a great variety of structures occur in this 

 connection. 



