THE YOUNG NATURALIST. 



limestones were forming were eight inches 

 in circumference. The Radiolarice are 

 smaller than the last, but the shells are 

 made of silica or flinty substance, and some 

 of them have silaceous spicules or needles 

 running through their substance, thus 

 possessing some of the characteristics of the 



mm® 



Holtenia Carpenteri, one of the Sponges, 

 one-third nat. size. 



true sponges. Sponges (Spongiclce) used to 

 be considered plants, but they are now 

 placed among animals. They are made 

 up of little silaceous and calcareous (limy) 

 spicules or needles — the skeleton, which 

 is invested with the living jelly-like mass. 

 There is also a curious system of water- 

 circulation through the substance of the 

 sponges. If you examine a sponge you 

 will find that there are some elevated 

 openings, and around them are smaller 

 openings. The water enters in at these 

 small openings, and, after passing through 

 little chambers where the true sponge 

 animal resides, each with a little thread or 

 cilium with which they lash the water 

 and so keep up the current, it comes out 

 at the larger openings. The common 

 household sponge is only the skeleton, the 

 protoplastic substance having decayed 

 away. There are various kinds of sponges, 

 some small species of which are found in 

 fresh water. Some very beautiful ones are 

 found in the Madeira Islands, and other 



places. One kind, called the glass ropejti 

 sponge, is like a flower upon a stalk, the|r 

 stalk being covered with little coral polypsjK >• 

 and it was long a contested point whetheriT 

 at was a true sponge or a coral. Another,jfi: 

 and perhaps the most beautiful kind, isjti 

 called Venus' flower basket (Euplectellce),^. 

 and its skeleton is composed entirely oifc " 

 silaceous spicules. It is built up in thejh 

 form of a hollow network tube, aboutjjif 

 eight or ten inches long with a covering aljji . 

 the top and is one of the most pretty oi>r ; 

 objects. This brings us to the third ordera*::;:- 

 — the Infusoria, so called from the facto 

 that they readily appear in infusions o% 

 hay or other vegetable or animal substance) h:;., 

 Some people might say they were producecj^: 

 by spontaneous generation, while the malt: 

 jority would say that the germs were therakrcti: 

 before, and that the addition of watejl Hie 

 only developed them. They multiply hifeud: 

 fission or by budding, the bud after a timi p: 

 dropping off, and after swimming abouj k:. 

 for some time, settles down and produce Moi 

 a separate organism. The first clasp 

 ( Surtoria ) throw out pseudopodia like th; 

 Rhizopoda but these differ in being holloa 

 tubes with club shaped discs at the enc 

 each one of these discs serves as a mout 

 for catching food, which passes down th 

 tube into the interior of the animal. Thj 

 Infusoria differ from the Rhizopoda i 

 having a sort of rudimentary mouth. Ti 



! t 



top 



ML 



P* 

 Mi 



m 



In 



bi 



^Epistylis Vorticella, one of the Ciliata 

 showing bud highly magnified. 



second class is called Ciliata because i 

 the animals swim about, or gain food 1 

 means of cilia, and many are like flowe 

 at the end of a stalk, the stalk being fix 



