208 AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



females, in which process the roughened pads on the hands afford 

 firm attachment. This occurs in the water. The ova burst out 

 from the ovaries, are taken up by the ciliated funnels of the 

 oviducts, and pass down those structures to the uteri, receiving 

 on their way gelatinous investments. Here they are aggregated 

 into " clumps," and expelled by the contraction of the muscle in 

 the uterine and cloacal walls. As they are extruded from the 

 body, sperms are shed over them by the male. Fertilization 

 occurs in the usual way by fusion of a sperm with each ovum. 



8. Muscular System. In a tadpole there are lateral muscles 

 divided into myomeres, as in a fish, but only traces of this seg- 

 mentation are to be found in the adult. The muscles are very 

 numerous, and have a very complicated arrangement. The 

 following table will give a rough notion of their classification 

 (after Huxley) : 



A. Muscles of Head j EpisMetal, superficial to the endoskeleton. 

 and Trunk. \ flyposkeletal, within the enduskeleton. 



B. Muscles of Limbs. 



Intrinsic, taking origin in the limbs themselves 



(including girdles). 

 Extrinsic, taking origin outside the limbs. 



The firm endoskeleton affords points of attachment, and this is 

 often effected by the intermediation of cord-like tendons, almost 

 entirely made up of white connective-tissue fibres. The firm 

 sheaths, aponeuroses, by which muscles are covered, may also 

 serve for the attachment of other muscles. This is best seen in 

 flat muscles, such as some of those forming the abdominal wall. 



The muscles are made up of bundles of transversely striated 

 fibres, each of which is invested by a delicate sarcolemma, and 

 contains numerous muscle-corpuscles i.e., nuclei surrounded by 

 small quantities of protoplasm. These fibres also exhibit longi- 

 tudinal striations. 



From a physiological point of view the muscular tissue of 

 Vertebrates is divided into (1) Involuntary, not under the 

 control of the will, including the unstriated fibres of the viscera 

 and blood-vessels, as well as the striated fibres of the heart ; and 

 (2) Voluntary, under the control of the will, including the 

 striated fibres of the ordinary muscle. 



The minute structure of muscle and its physiological import 

 have long been much vexed questions. The views here adopted 



