ZOOLOGY AND BOTANY^ MICROSCOPY, ETC. ' 585 



first a broad hyaline area, in which the filaments of the network are only 

 indistinct. As the nuclear network grows, the surrounding protoplasm 

 becomes more and more indistinct, while the fibres of the successive 

 nuclei fuse with one another. Finally, the two upper rows of nuclei 

 unite, and we get the neural reticulum. This, in sections of each half 

 of the ganglion, has the form of three plesiform areas, two inferior and 

 one superior ; the lower are separated from the upper by the cytoplasm, 

 in which the processes of the ganglia form the transverse commissures. 



The youngest ovaries of Gordiidfe are characterized by the absence 

 of lateral lobes and ovarian cavities; in the older ovaries each lobe 

 consists of similar cells, and has a racemose form ; their cavities com- 

 municate directly with the lumen of the receptaculum ovorum, the walls 

 of the latter being continuations of the epithelium of the ovary. The 

 development of ova does not occur in all the lobes, but in a few only ; 

 it is very simple, some epithelial cells of the ovarian lobes growing con- 

 siderably, their protoplasm being converted into yolk-granules, and the 

 nuclei increasing a little in size ; but the change appears to be effected 

 very rapidly. It is very probable that several epithelial cells are 

 simultaneously converted into ova, the consequence of which is that the 

 eggs take on a shield-shaped or polyhedral form. The mature ova pass 

 directly from the ovarian tubules into the receptaculum ovorum ; this 

 last is provisionally regarded as a modified excretory organ, but this 

 supposition must be tested by embryological investigations. In well- 

 preserved material it is possible to see that the receptaculum has proper 

 walls. The atrium, the oviduct, and the seminal pouch have probably 

 all arisen from an evagination of the hind-gut. The cloaca of O. 

 tolosanus is much more evident than that of G. Presslii. 



In appendices the author deals with some recent statements of 

 M. Villot, and with Herr Nansen ^ account of the nervous system of 

 Myzostoma. 



Anguillulidse of the Onion.*— M. J. Chatin, who has given an 

 account of the disease caused by Tylenchus putrefaciens in the edible 

 onion (^Allium Cepa), has continued his observations on the nematode 

 parasites of this vegetable. He has been able to recognize three species, 

 Pelodera strongyloides, Leptodera terricola, and T. putre-faciens. The 

 last of these aj^pears to be the cause of the disorganization and destruc- 

 tion of the bulb, and the premature destruction of the appended organs. 

 The first two are only met with in the superficial parts of the plant, or 

 only follow T. putrefaciens into the deeper parts ; they are simple 

 " saprophytes." 



Tylenchus devastatrix-t — In a third communication on the natural 

 history of Tylenclms devastatrix, Herr Eitzema Bos discusses the diseases 

 which this Nematode causes on plants. He discusses first the disease of 

 rye, marked especially by the abnormal swelling of the stem base. The 

 relevant literature, the nomenclature, and the symptoms are noted, and 

 the disease is illustrated in two cuts. He emphasizes the fact that it is 

 by the soil that the worms are perpetuated, and notes how the activity 

 of the 'parasites themselves, the action of wind and water, and even 

 human agencies effect propagation. In the second place he discusses 



* Comptes Eendus, cvi. (1888) pp. 1431-3. 

 t Biol. Centralbl., viii. (1888) pp. 129-38. 



