732 SUMMA-BY OP CURRENT RESEARCHES RELATING TO 



formation of colonies in the latter group will not hold, since it is 

 possible to pass from Ciona — a typical simple Ascidian — to Distoma 

 and the very heart of the compound Ascidians through the following 

 series of forms, which shows a perfect gradation of these characters : — 

 Ciona, Bhopalcea, Edeinascidia, Clavelina, Diazona, Ghondrostachys, 

 Oxycorynia, Distoma. The formation of common cloacal cavities, 

 canals, and apertures cannot be considered as a diagnostic feature of 

 the compound Ascidians, as there are forms considered by all autho- 

 rities as Synascidise, such as Ghondrostachys, Diazona, Distoma, and 

 others, in which the atrial apertures of the Ascidiozooids open inde- 

 pendently on the surface of the colony, and no common cloaca is 

 formed. 



The characters taken from the condition of the test, break down 

 like the others. In the first place, in passing along the series of 

 forms connecting Giona and Distoma, we encounter all stages between 

 a distinct test or tunic for each individual, and a common mass in 

 which a number of Ascidiozooids are imbedded. And secondly, the 

 remarkable group " Polystyelae " presents many of the characters of 

 highly differentiated simple Ascidians (the Cynthiidse) along with the 

 supposed Synascidian feature of a colony composed of many Ascidio-. 

 zooids completely buried in a common test. 



Digestion in Salpa.* — Dr. C. S. DoUey combats the view of Korot- 

 neff as to the existence of a large amoeboid cell or plasmodium in the 

 oesophagus or stomach of Salpa which carries on a form of parenchy- 

 matous digestion of the food passing the resulting chyle into the 

 walls of the intestine by means of its pseudopodia. 



Dr. DoUey has observed the appearance in the intestines of Salpa, 

 which had been described by the Eussian author, but he suggests an 

 entirely different interpretation. In Salpa we find a large branchial 

 sac, representing the true pharynx, at the posterior portion of which 

 is the stomach. The endostyle, or thickened bottom of a fold or 

 groove of the branchial sac, throws out a supply of mucus, which 

 covers the surface like a curtain, and in which nutritive particles 

 finding their way into the animal are imbedded. The food is carried 

 back by cilia, and the mucous sheet is wound up into a thread, which 

 can be traced into the oesophagus, and from there to the stomach . 

 This mucous exudation is the amoeboid cell of Korotneff. 



Fresh-water Bryozoa.f — K. Krapelin has been able to find, in 

 the neighbourhood of Hamburg, examples of all the genera (except 

 perhaps Lophopus) of Bryozoa that are known to inhabit the fresh 

 waters of Europe. In addition to these he found large masses formed 

 by colonies of Pectinatella magnifica, described by Leidy as living 

 near Philadelphia. In this genus, in Cristatella, and possibly also 

 Lopliopus, the statoblasts are set free on the death of the colony. 

 The author asks for the assistance of correspondents for the purpose 

 of making a more complete investigation into the biology and geo- 

 graphical distribution of these animals. 



* Proc. Acad. Nat. Sci. Philad., 1884, pp. 113-5. 

 t Zool. Anzeig., vii. (1884) pp. 319-21. 



