THE DEVELOPMENT OF PROTOZOA. 285 



increasing in number and consequently diminishing in size (D) 

 as time passes on. By and by, however, having become a mul- 

 titude in number, and exceedingly diminutive in proportions, they 

 cease to divide. 



After the egg is thus converted into what is called the mul- 

 berry state, the process of developing the organs begins, and is 

 carried out in a manner which varies according to the type to 

 which each several animal belongs. 



PROTOZOA. 



It is so short a time since it was discovered that the Protozoa 

 reproduce themselves through the mediation of the egg-phase, 

 and the subject is such a difficult one to follow out, on account 

 of certain peculiarities in the habits of many of the members 

 of this group, that we have only been able to get a glimpse of 

 the mode of development which is peculiar to this class. In 

 fact, it will not be possible, on this occasion, to do more than in- 

 dicate two or three phases, at most, in the development of the 

 young from their earliest to their latest period of growth. As 

 far as they go, however, they clearly demonstrate that the pro- 

 cess of development is totally unlike that of any of the other 

 grand divisions, and in strict conformity with the typical idea 

 upon which the Protozoan organization is based. 



The Protozoa consist of two clearly marked groups. The 

 one begins with Amoeba, (p. 9, fig. 1,) Difflugia, (p. 11, fig. 2,) 

 Cornuspira, (p. 13, fig. 3,) and Rotalia, (p. 14, fig. 4,) and rising 

 through the successively higher forms, such as Sponges, (p. 41, 

 fig. 21,) Actinophrys, (p. 44, fig. 22,) Lithocampe, (p. 49, fig. 23,) 

 and Zooteira, (p. 50, fig. 24,) finally culminates in Podophrya, 

 (p. 51, fig. 25). The members of this group do not possess 

 vibratile cilia as a means of locomotion in their adult state, 

 but are dependent altogether upon certain organs of adhesion 

 for this purpose, and for seizing their food. Certain forms have 

 been classed together under the name Suctoria, on account of 

 their habit of sucking the juices of their prey through their 

 feelers. Such a one is Podophrya (fig. 25) ; but as I conceive 



