THE STYLASTEES. 293 



The stomach and finger zooids contain muscular fibres, and the nematocysts or thread-cells have a 

 spiral within them, with part of it jagged with a thorny part. Others have three barbs on the thread. 



The hard part of the Millepore is called the coenosteum. Unfortunately, the method of 

 reproduction had not been ascertained by Prof. Moseley, to whom we owe the very exact description of 

 these interesting things, which were formerly, before Agassiz saw the zooids, considered to be true 

 tabulate Corals. Certainly it is only the part of the coenosteum above the uppermost tabula that is 

 alive ; all below was so once, and has died. 



FAMILY STYLASTERID.E (WITH AMPULLA). 



These have the pores with a style or calcareous spiny projection. Ampullae, or blister-like 

 swellings on the surface, contain the male elements and large planulse. 



The Stylasters were named after small red-coloured, more or less fan-shaped, branching coral-like 

 substances, on which are numerous groups of pores sur- 

 rounding central cavities, having a projection at their 

 bottom. Until Moseley examined them, they were in- 

 cluded in the Stony Corals, and the divisions between the 

 pores were considered to be septa. He has proved that 

 the family, which comprises many genera, belongs to the 

 same sub-order as the Millepores. The hard part of the 

 animal is composed of reticulations of tubes, and a gas- 

 terozooid occupies the central pore space, and dactylozooids 

 the surrounding circlet of pores. The hard part consists 

 of carbonate of lime to a considerable extent, and is formed 

 by the deposit of it in the substance of the outer skin, or 

 ectoderm, of the canals or tubes. The canals open into the 

 pores, which are really cylindrical pits, and at the bottom 

 of each are a few large canals and their openings. Some 

 genera have a projection, or style, more or less brush-shaped, 



on the base of the floor of the cavity for the gasterozooid, and MILLEPOKA. (After 



resting on a partition or tabula, of which there may be more The gasterozooid r ^}j d a d the dactylozooids 



than one. Small, more or less rounded, projections occur 



011 the surface of the hard part of the animal, and they are the domes covering spaces. These open 

 by slits or get very thin at the surface, and contain the male reproductive elements, or a most remark- 

 able worm-like embryo, which is termed a planula. The planula is large and cylindrical, and being 

 curled up, is larger than the cavity in which it has developed out of an ovum ; and this cavity is large in 

 relation to the circlet of pores in some genera. A mature planula is a quarter of an inch in length, and 

 has a transparent gelatinous-looking outer skin, or ectoderm, and a dark-coloured inner, or endoderm. 

 It looks like a worm, and is probably covered with cilia, and there are polygonal markings on the body, 

 and nematocysts. No internal organs exist, and this young form is solid within. It escapes and 

 settles down after leading a free-swimming life, but how the future growth proceeds is not known. 



The dactylozooids of all the genera of the family have simple tentacles, which retract, and the 

 gasterozooids are flask-shaped, and may or may not have club-shaped tentacles on them. 



These interesting Hydrocorallinfe are found very widely distributed from 10 to 750 fathoms' 

 depth in the North and other parts of the Atlantic and the Pacific Oceans. The West Indies, the 

 coasts of Brazil, and the Japanese Seas are common localities. They may be arranged in two groups. 

 In one the pores occur in regular circlets, or cycle systems, and the genera may again be subdivided 

 into those which have styles present at the bottom of the gasterozooid, and also of the dactylozooid pores. 

 Stylaster and Allopora belong to this subdivision. Of those with styles only present in the gastero- 

 zooid pores, Stenohelia is an example ; and of those without any styles, Astylus and Cryptohelia are 

 examples ; the last-named genus has a remarkable lip in front of the circlet of poi'es. 



In the second group, the pores for the dactylozooids are either of one or two kinds, and a group 

 of genera belong to each. Pliobothrus and Errina are examples of the first, and Spinipora of the 

 latter condition. 



