286 ZOOPHYTES. 



that stage of the progeny wherein it can be commonly exposed without 

 injury, and is most frequently presented to view. 



The ovum is an organic formation, usually generated within the pa- 

 rent, as in all the larger and more perfect animals, and with few excep- 

 tions, it is produced externally. It seems originally an inert mass, which 

 unless rendered prolific, shall ever remain barren and unproductive. 



With the various theories of the effective process, whereby the latter 

 may be averted, I purposely abstain from interfering, farther than to ob- 

 serve, that in my opinion, no arguments sufficiently relevant are yet offered, 

 to establish that those mysterious invisible animals belonging to the 

 stronger sex, are instrumental in perpetuating the race. 



No subject, however, can be of equally curious and interesting inves- 

 tigation, than how living animals are derived from each other. 



The ova of most creatures are generated internally, as if it were ne- 

 cessary for the security of their tender elements. But, in certain tribes of 

 the zoophytes, they are generated externally, and sometimes in great pro- 

 fusion. 



The ovum is then protected by an integument, often affording little 

 resistance, as in the Tubularia : or greater, as in the Sertularia, when 

 lodged in a pod or capsule. The progress of the former may be traced 

 as advancing from lower stages to maturity. But the early state of the 

 latter, in as far as I understand, has not been yet detected. 



Whatever be the original form, substance, or nature, of that which 

 becomes afterwards recognizable as an embryo, or foetus, it is at length 

 contained in an ovum, along with a quantity of matter serving as pabu- 

 lum, to sustain it throughout its advances until exclusion. 



Meantime many important changes are undergone. 



If a germ or a speck from depositation of the parents be the nucleus 

 of the ovum, which is merely enlarged and modified in the course of in- 

 crement, the earliest sensible form seems to be spherical, in preparing it 

 for receiving the institution of life. 



If in this state the early ovum, with the germ, be soft and duc- 

 tile, expansion in one direction more than in the other, may render it 

 oyoidal. 



