Memoirs: On a New Genus of Synascidians from Japan

Sarcodidemnoides misakiense, Oka and Willey. Generic Characters.--Colony (or cormus) forming very thick lobose masses, laterally compressed; sessile, but not encrusting. Excurrent orifices placed on the tips of the knoll-like prominences. Ascidiozooids very numerous, not arranged in systems; branchial sac with four rows of stigmata; canal system complicated, differentiated into peripheral and central portions. Specific Characters.--Atrial apertures of Ascidiozooids simple pores without teeth or languet; spicules fairly abundant, extremely delicate, confined to a thin layer near surface of test. Test gelatinous, containing numerous bladder-cells, crystals, fusiform cells, and pigment concretions. Stomach of Ascidiozooids vertically placed; surface of attachment of colony narrower than the free portion. Colour, brilliant red. Habitat.--Moroiso, Japan, between the tide-marks. N.B.--Since the above was written I have seen for the first time the exhaustive work of Fernand Lahille, entitled ‘Recherches sur les Tuniciers des côtes de France,' Toulouse, 1890. Lahille devotes considerable attention to what have been spoken of above as tentacle-like processes of the larva, figures them in many larvæ, and gives an excellent figure of the metamorphosing larva of Styela glomerata. He gives an opinion as to their significance which I cannot entirely endorse in the light of my own researches on the "Postembryonic development of Styela," commenced last August at Plymouth. However, I hope to return to this question on a future occasion. Lahille raises an objection to von Drasche's genus Didemnoides on the ground that the thickness of the cormus is not an anatomical character, and that the distinction between thick and thin colonies is a purely subjective one. There is no doubt some truth in this; but the difference between a compound Ascidian which possesses, say, a very few spicules, and one which possesses none at all, would appear to be no more fundamental than that between a colony whose mode of growth resulted in the production of a fleshy mass and one which grew in the form of a thin leathery crust. As stated above, von Drasche intends by Didemnoides a fleshy form of Leptoclinum, the test containing spicules, and the Ascidiozooids having four rows of stigmata in the branchial sac. Lahille, on the contrary,applies the name Didemnoides to those Didemnidse which are characterised by the absence of spicules, and the possession of three rows of stigmata in the branchial sac. The compound Ascidian which we have described above has spicules in the test, and four rows of stigmata in the branchial sac. But as it would be too absurd to call the new form "Sarcoleptoclinum," we shall persist in regarding the genus Didemnoides from the point of view of von Drasche.--A. W.