ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 817 



latter they are parallel to them ; hence in the former the great excre- 

 tory canal runs from the subdermal cavities to the vents, while in the 

 latter they run under the subdermal cavities ; the excretory canals 

 are furnished with circular folds, and consist of a layer of epithelium, 

 and beneath of "? muscular fibrillae,' partly longitudinal and partly 

 transverse " ; the action therefore upon the contents will be like that 

 of the human intestine, and tend to drive them along the tube. 



Development of Spongilla.* — A further communication on this 

 subject by Dr. A. Goette is the fourth of his series of notes on the 

 development of SpongiUa ; he criticizes the result of Dr. W. Marshall 

 in the following points. The gemmul® do not arise from special 

 " trophophores," but from a portion of the parenchym, together with 

 the neighbouring ciliated chambers and canals ; the gemmulse do not 

 consist of three layers ; the cavity of the young sponge has been 

 stated by Marshall to commence with a central excavation from which 

 the canals grow out ; in reality it would seem that the cavities appear 

 separately, and that the ciliated chambers are not outgrowths of, and 

 have no relation to the rest. SpongiUa lacustris has no seasonal 

 alternation of generations. 



New Fresh-water Sponge.f — Mr. E. Potts describes under the 

 name of Heteromeyenia pictonensis, a new sponge from Nova Scotia ; it 

 is closely allied to H. Hijderii, but differs in the characters of the 

 birotulate spicules, which are as follows : " Shafts mostly smooth, 

 though sometimes bearing a single spine, irregularly cylindrical, 

 but rapidly widening to support the rotules, which are large, umbonate, 

 nearly flat, and finely lacinulate at their margins, occasionally 

 bearing spines." 



Protozoa. 



Protozoa. J — Prof. E. Eay Lankester has a very fully illustrated 

 article on the Protozoa, in the course of which he discusses a number 

 of interesting points. 



With reference to the nature of the first protoplasm which was 

 evolved from not-living matter, he expresses his belief that it was 

 without chlorophyll, or in other words, did not possess the power of 

 feeding on carbonic acid. Apart from their elaborate fructification, 

 the Mycetozoa represent more closely than any other living forms 

 the original ancestors of the whole organic world. " Thus then we 

 are led to entertain the paradox that though the animal is dependent 

 on the plant for its food, yet the animal preceded the plant in 

 evolution." 



The I'rotozoon-ccll-individual is then compared with the typical 

 coll of animal and vegetable tissues ; a nucleus is thought to bo 

 probably always present. 



• Z<X)]. Anzoit;., viii. (lS8.j) pp. .S77-80. 



t Ann. and Mafj. Nat. liist., xv. (1885) pp. 425-C. 



X Ericjcl. IJrit, vol. xix. (1885) pp. 830-CU. 



