ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 561 



in other Echinoderms. The wall of the body and the wall of the gut 

 in Echinoderms is formed of three layers, of which the median one 

 represents the schizocoel and is composed of lacunar tissue ; calcareous 

 formations are confined to the other two. The haemal system is not a 

 closed system apart from the schizocoel, but remains freely in communi- 

 cation with it. 



Coelentera. 



Free-Swimming Hydroid. * — A. Dendy found on the beach near 

 Christchurch a living specimen of what must be called a free-swimming 

 hydroid, — perhaps an aberrant Tubularian, related to Corymorjiha and 

 its allies. Dendy calls his prize Pelagohydra mirabilis g. et sp. n., and 

 gives this diagnosis: — Hydroid solitary, free-swimming ; the proximal 

 part of the body modified to form a float, supported internally by a 

 system of radiating membranes of endodermal origin ; the distal portion 

 forming a flexible proboscis, with the mouth at its extremity. Gastral 

 cavity continued from the proboscis into the float in the form of endo- 

 dermal canals, from which arise branching stolons. Tentacles filiform, 

 scattered over the surface of the float and in whorls around the mouth. 

 Medusae developed on stolons between the tentacles of the float ; quadri- 

 radiate, symmetrical, probably with gonads in the wall of the simple 

 manubrium ; tentacles in four per-radial groups of five (possibly more 

 in the adult). 



The adaptation of a hydroid type to free-swimming life, such re- 

 markable structural features as the endodermal canals from the gastral 

 cavity and the float with its extraordinary supporting membranes, and 

 the high degree of histological differentiation, make Pelagohydra a re- 

 markably interesting organism. 



Budding in Larvae of Gonionema murbachii.f — H. F. Perkins 

 describes a very interesting and quite unique case — a process of non- 

 sexual multiplication by budding in the solitary larvae of a Hydro- 

 medusan. The buds are produced singly and become detached as 

 planulae. From the planula stage onward, the asexually produced larvae 

 repeat the ontogeny of the sexually produced forms. The author also 

 reports an instance of apparent transverse fission, in which the ccelen- 

 teron had undergone complete division. 



Aggregated Colonies in Madreporarian Corals.} — J. E. Duerden 

 discusses the occurrence of colonies, which von Koch called " aggre- 

 gated," formed through the secondary fusion of individuals which were 

 originally distinct, as apart from most Anthozoan colonies which are 

 produced by the budding or fission of a single individual. Von Koch's 

 example was found in specimens of Balanophyllia verrucaria, a Medi- 

 terranean coral which usually retains a simple habit ; Lacaze-Duthiers 

 described and figured a similar aggregated state in Caryophyllia ; certain 

 forms of the rugose coral Streptelasma (Palseophyllum) divarkans 

 Nicholson seem also to be aggregated colonies. Duerden has found in 

 the common West Indian coral, Siderastrsea radians Pallas, actual 

 instances of colony formation by the fusion of originally free, distinct 



* Quart. Journ. Micr. Sci., xlvi. (1902) pp. 1-24 (2 pie.). 

 t Johns Hopkins Univ. Circ, xxi. (1902) pp. 87-9 (11 figs.) 

 X Amer. Nat., xxxvi. (1902) pp. 4G1-71 (3 figs.). 



