316 ANNUAL OF SCIENTIFIC DISCOVERY. 



in the Indian Ocean and China Seas, is caused by a minnte alga, 

 referable to Tricliodesmium, a genus of Osc'dlatorice. The plant 

 consists of short fihinients, composed of a single line of cells, 

 combined into a cylindrical unbranched fibre ; many are aggre- 

 gated into little bundles, having the appearance of a sheaf or a 

 wedge, according as they are in close contact either at the middle 

 or at one end. 



The red discoloration seen in the Red Sea, Persian Gulf, and in 

 the north Pacific, is caused by one or more closely allied species 

 of Trichodesmium. 



ANCESTRY OF INSECTS AND CRUSTACEANS. 



Dr. A. Dohrn, of Jena, has lately described anew fossil insect, 

 which he calls Eugereon BoecJdngi, which has characters interme- 

 diate between those of the hemiptera and neuroptera, and must, 

 he thinks, be genetically related to the two orders, — not that it 

 was the common ancestor of these two groups, for the neuroptera 

 are found alongside of it, but that at a period not much earlier 

 an insect form existed completely intermediate between the neu- 

 roptera and hemiptera, from which these two orders were differ- 

 entiated and from which Eugereon also was descended, not having 

 become so much modified. 



According to Prof. Haeckel, insects, spiders, centipedes, and 

 Crustacea must have had a common ancestor. The ancestral form 

 of the Crustacea is known, appearing in their development as the 

 Zoece. The ancient adult Zoe(B or Zoepoda, as he calls them, 

 flourished early in the Silurian period according to him, and it 

 was probably about the Devonian epoch that certain zoepods 

 were naturally selected for a terrestrial life, developed tracheae, 

 and became Protracheata, or progenitors of all the great tracheif- 

 erous group of the aiticulate-limbed animals; while those which 

 remained in the water are the ancestors of the branchiferous forms 

 called crabs, lobsters, and shrimps. Whether any Protracheatce 

 exist still is, says Haeckel, doul)tful ; perhaps the Solifugce, a 

 strange group of aberrant spiders, and also those insects which 

 have no wings (not through disease as in many cases, but by their 

 progenitors never developing them), represent amongst to-day's 

 fauna the protracheata of the past. — Quart. Jour, of ScL, Oct., 

 1868. 



A VIVIPAROUS ECHINODERM. 



Dr. Ed. Grube describes an echinoderm from the Chinese Seas 

 under the name of AnocJiamis, which produces young echini like 

 itself, having spines, feet, and even pedicellarise. These young, 

 though having a general resemblance to the parent, are not quite 

 the same in detail, and must undergo modification with growth. 

 This discovery is of remarkable interest, for it adds one more to 

 the many diverse methods of reproduction known among echino- 

 derms, and completes the parallel which they present to the 



