128 University of California Publications. izoology. 



This kind of onion was not recognized by Harmer, and as a 

 consequence the instances which he offers as probable early 

 stages of an ovicell are somewhat doubtful ('93, PI. 22, Figs. 1 

 and 2). This is especially true of Fig. 1, which is probably an 

 instance of this second relation. 



The partial development of an embryo in connection with a 

 polypide is interesting for two reasons. In the first place, it 

 probably points to a more primitive method of reproduction, and 

 in the second place, it is important for the light it throws on the 

 time and place of fertilization. 



In regard to the indications of more primitive conditions, it 

 is clear, aside from the question of the origin of the ova. that 

 in Tubulipora (Harmer, '98) ova occur in many of the zocecia. 

 Moreover, in this genus any zooeeium may become an ovicell, 

 and usually several zocecia of a colony become thus transformed. 

 In the constant occurrence of eggs in the individual zocecia. and 

 in the direct transformation of the latter into ovicells, Tubulipora 

 shows the least specialized condition of any Cyclostome whose 

 history is known. In Lichenopora an ovum is found only in 

 that young zooeeium which becomes the ovicell of the colony, 

 and which Harmer designates as the fertile zooeeium. In this 

 case specialization may be considered to have gone a step further 

 in setting- off a certain zooeeium to perform the function of an 

 ovicell, and perhaps to produce the single egg which comes to 

 maturity. In Crisia specialization has proceeded so far that 

 the ovicell is at no time a zocecium, although from its position 

 in the internode it must be considered homologous with one. 

 While the ova in this genus are a colonial production and always 

 originate at the anterior edge of the branch, they are occasionally 

 found in the individual zocecia. Such instances may be regarded 

 as representing an early tubuliporidan stage, or possibly a more 

 primitive stage in which each zooeeium brought at least one ovum 

 to maturity. 



In regard to the time and place of fertilization, it may be 

 said that since Crisia is dioecious the question arises as to the 

 time when, and the manner in which the spermatozoa reach the 

 ova. According to Harmer, fertilization probably takes place 

 after the egg has been inclosed by its follicle and after the ovicell 



