498 CHARACTERS OF INVERTEBRATE ANIMALS 



they are plants or animals (Gk. mykes, a fungus; zooit, an animal). 

 Indeed, like Volvox and its allies, they will be found described 

 in most text-books, both of botany and zoology. A good example 

 is the so-called "flowers of tan" {^thalium) (fig. 301), which is 

 to be found in the form of sulphur-coloured net-works of proto- 

 plasm creeping slowly over heaps of spent tan, and attaining 

 a considerable size. At a certain time this organism produces 

 little capsules in which a number of small hard-coated repro- 

 ductive bodies known as spores are formed. From these escape 

 little fragments of protoplasm, which are at first something like 

 flagellate protozoans, for each of them possesses a single 

 flagellum, while later on they assume the shape of minute 

 amcebse. A number of these fuse together to form a creeping 

 net-work. 



In the Amoeba group we may also include one of the simplest 

 known kinds of Protozoa, a minute marine animal — Protomyxa 

 aurantiaca (fig. 302) — found on the coast of the Canary Islands. 

 In colour and appearance it resembles a small individual of the 

 tan-flower organism, but no trace ot a nucleus was observed by its 

 discoverer. After leading an active life for some time the body 

 contracts into a spherical form and becomes surrounded by a 

 firm investment. The protoplasm then divides up into a number 

 of fragments, each of which possesses a single flagellum. These 

 are liberated by the rupture of the protecting investment, soon 

 assuming the shape of little amoebae, of which numbers fuse 

 together to form an adult. 



Group 3. — Gregarines (Sporozoa) 



This third and last group of the Protozoa has been modified 

 by the parasitic habit. The body is covered by a firm cuticle, 

 but cilia as well as pseudopods are absent. A good example is a 

 form (Clepsidrina blattarum) (fig. 301), found within the alimentary 

 canal of the Cockroach. The elongated body, when very young, 

 is attached by a hooked narrower end to the lining of the' cock- 

 roach's intestine. Later on, the hooked end is shed, the animal 

 becoming free. A nucleus is discernible within the protoplasm, 

 but no pulsating vacuole. As the name indicates, the group 

 is characterized by the presence of those specialized reproductive 

 cells called spores, which are more commonly met with in plants 



