ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 29 



by the aid of the horizontal Microscope. Diatoms and desinids are 

 caught by the currents set up by the cilia of the tentacular crown, and 

 passed into the foregut, at the base of which they lie until a quantity of 

 them have been collected. By a wave-like constriction of the foregut 

 they are then passed through the circular valve into the stomach. By 

 the peristaltic action of the stomach the food is driven backwards and 

 forwards ; the food is next impregnated with the enteric secretions, 

 and then begins to be absorbed. A fresh quantity of food again enters 

 from the oesophagus, and the indigestible portions of the first mass are 

 driven into the rectum. With regard to the reproductive apparatus, the 

 author is confident that the funiculus is formed solely by the mesoderm. 



Little can be added to Nitsche's account of the nervous system ; 

 osmic acid preparations showed that the cells composing the ganglion 

 have rather large nuclei, and especially those that are central. The 

 ganglion is invested by a thin mesodermal layer, by means of which 

 ,it is attached to the upper part of the pharynx ; as there is no meso- 

 dermal layer between the pharynx and ganglion, the latter appears to be 

 constricted oft' from the pharyngeal wall. "With regard to a colonial 

 nervous system, the author remarks that it may be thought that if ever 

 it be present in a fresh-water Bryozoon it must be found in Cristatella, 

 but he has convinced himself that the creeping movements are effected in 

 a way which makes such a system superfluous. They are the resultants 

 of the pressures exerted by the separate animals on the pedal disc, and 

 their direction is caused by the direction of the separate animals. 



Herr Verworn has investigated the development of the statoblasts, 

 and finds that at a definite point of the funiculus the epithelial cells 

 increase, and form a small swelling, which presses on the lumen ; one 

 cell now passes into the lumen and becomes an egg-cell, while the others 

 form a follicle ; the egg goes through a regular process of cleavage, 

 the final result of which is a solid morula; it is clear from this that 

 the statoblasts have not the nature of buds, and it may be said that the 

 statoblasts are parthenogenetic winter ova which, unlike the fertilized 

 ova, are developed on the funiculus. 



Arthropoda. 



Primitive Insects. * — Prof. B. Grassi continues his researches on the 

 ancestors of Myriopods and Insects. He calls attention at the outset to 

 an overlooked memoir by Meinert, which describes the genital organs 

 of Machilis. Grassi's present memoir begins with a classification of 

 Thysanura, which includes the four families Campodeadas, Japygidae, 

 MachilidaB, Lepismidse. The latter comprise three genera, Nicoletia, 

 Lepismina, Lepisma. The characters of the family and of the three 

 genera are given in detail. He then proceeds to give a useful summary 

 statement of the characteristics of the species. 



The next chapter is devoted to an account of the anatomy of Lepisma 

 and Lepisrnina, which he compares with his previous results, gained from 

 the investigation of Machilis and other forms. 



Prof. Grassi next discusses the musculature of Thysanura, seeking to 

 discover whether the Thysanura once had wings or not, and whether 

 there are any traces of the previous existence of abdominal appendages. 

 He finds in the musculature no evidence whatever to warrant the first of 



* Bull. Soc. Entomol. Ital., xix. (1SS7) pp. 52-74. 



