72 



LUCERNARI^ AND THEIR ALLIES. 



vesicle and the yolk form an organized Avhole, the aimtml-egg, representing, in its 

 lowest condition, the aniiiud and the vegetative compound which we call a zoon. 



144:. The fact that in some animals, e. (/., the Vermes, Nematoda, and Trema- 

 toda, the germinal vesicle originates in a separate division of the ovary from that 

 in which the yolk is developed, does not invalidate our theory, but, on the contrary, 

 tends to sustain it. The ovarian cjtoblasiemon furnishes the material to start with, 

 in any case ; the albuminous substance on the one hand and the oleaginous on the 

 other, and it is only a question of degree whether these two elements are brought 

 too-ether particle by particle and then each develops its peculiarities by consenta- 

 neous action in time and place, or each masses its atoms in a separate division 

 of the ovary and elaborates its characteristic qualities there, and then are united 

 into one mass. In eitlier of these two extreme cases, the moment the parti- 

 cles of albumen and oleaginous matter come together they assume certain rela- 

 tions which we have indicated by the term iwlarity, and that is the beginning of 

 the animal egg. The direct connection of the polarity of the so-called egg with 

 the polarity of the later stages of the animal offers unmistakable evidence that the 

 first stage, i. <?., the egg-stage, is not to be separated from the second any more than 

 the second shonld be from the third. All are parts of what are necessary to make 

 up the life of the animal. Each stage has its functions, the egg-stage has its, and 

 so has old age ; and the first should no more be separated from the second or third 

 stage, because its functions Ure not identical with theirs, than the last, or old age 

 should be, because it fails in some of the offices of the one previous to it. 



145. The Spermatozoa (V\. xi, Jigs. 130, 131, 132). — The general outline of 

 tlic body is that of a cone which is twice as high as it is broad at its base. The 

 interior is perfectly homogeneous and colorless. It is not a fixed, rigid attitude 

 that we observe here, but one that varies considerably, especially about the apex 

 of the cone. At the latter point we find the body continued into two excessively 

 delicate filaments which are six or seven times longer than itself. These filaments 

 are very severe tests of the powers of a microscope. They are much more slender 

 than the so-called tail of the spermatozoon, and do not taper, but preserve the same 

 diameter to their tips, wliere they terminate abruptly. Upon seeing these lash-like 

 bodies coiling and twisting or swinging from side to side with every movement of 

 tJie highly flexible, conical apex, we are reminded of certain flagellate infusoria. 

 The broader end of the cone is indented where the tail is inserted. The tail is of 

 enormous length, measuring at least twenty times that of the body. It does not 

 taper, except for a short distance from its attachment. 



§ 20. A Young Haliclystus auricula, nearly j\th of an inch in diameter (PI. x, 



figs. 121, 122 A. to D., 123). 



146. Our records and illustrations of intermediate stages between the egg and 

 the adult are intended not so nuich to furnish the details of changes which take 

 place between youth and old age, as to explain the morpliogenic phases through 

 which tlie organs and certain regions of the body pass in order to reach their 

 perfection. Tlieir value, therefore, will be more appreciated upon contrasting them 



