PROTOZOA. 17 



have a Protozoan that is probably single when young and 

 colonial when adult, which illustrates an extremely inter- 

 esting phase of development in animal life. 



The Protamoeba, Bathybius, Protogenes, and Myxo- 

 dictyum belong to the simplest Monera; other genera of 

 this group illustrate further specialization in structure. 

 Archerina boltoni Lankester is represented in PI. 5, figs. 

 1,2. Fig. i may be the form that issues from the hard- 

 ened case or cyst. It consists of a spherical body with 

 long, motionless pseudopodia radiating outward from the 

 surface. A large vacuole is seen in the interior. This 

 organism is especially interesting because it contains 

 chlorophyl. The latter is confined to a single or bifid 

 corpuscle. No nucleus exists, but the chlorophyl cor- 

 puscle appears to take the place of the nucleus, perform- 

 ing a similar function in the process of reproduction. 

 The corpuscle usually divides into four parts followed by 

 the division of the surrounding protoplasm, until a colony 

 is formed (PI. 5, fig. 2, a small bit taken from a large 

 colony). This colony was decolorized, and the small 

 chlorophyl corpuscles appeared as in PI. 5, fig. 3, while 

 the large ones were undergoing division (see PI. 5, fig. 4). 

 The Haeckelina borealis (PI. 6), discovered by Meresch- 

 kowsky, shows a fixed or stationary Moner. The long, 

 solid stem by which it is attached is secreted by the pro- 

 toplasm, this secretion taking place constantly on one 

 part of the body which, when the stem is formed, becomes 

 the lower surface. This organism is without nucleus or 

 vacuoles, but several round, strongly refracting balls are 

 present in the protoplasm which are probably drops of 

 oil. The pseudopodia are short and delicate, and are 

 scattered over the whole surface. 1 



1 Biitschli places this form among the Heliozoa, although he says 

 vacuoles are wanting and presumably a nucleus, while there is no 

 differentiation of the protoplasm into an outer part, or ectosarc, and 

 inner part, or endosarc. Its striking resemblance to the Heliozoan, 

 Clathrulina, will be seen by comparing PI. 6 with PL 43, fig. 7, but 

 if the observations already made are accurate, the two forms are not 

 closely related genetically. 



