ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 229 



Natural History of Tylenchus.* — Dr. J. Ritzema Bos continues his 

 report on Tylenchus devastatrix Kiihn. (a) He discusses in the first 

 place its influence on the plants which it infests. Though it never pro- 

 duces what can be called galls, it causes hypertrophy of the tissues of 

 the plant. The hypertrophy seems to be due to some substance excreted 

 by the parasite, but it is possible that the mechanical action of tho 

 mouth, &c, may also be a factor. That the former, however, is at least 

 the main factor is suggested by a case of a Tylenchus found between, not 

 in the leaves of Hypnum cupressiforme, and yet causing a hypertrophic 

 abnormality. The author then notes the various degrees of plant disease 

 caused by different species of Tylenchus, which multiply at different rates, 

 &c. He thus contrasts T. devastatrix and T. scandens. The secreted 

 substance is only fatal to the plant when large quantities are present. 



(&) Latent life. The author cites some observations on the latent 

 life of T. scandens ( = Anguillula tritici). T. devastatrix seems to surpass 

 the former in this capacity, which is saying a good deal. The experi- 

 ments made by the author on ova, larvas, and adults, are described at 

 some length. Ova were kept dry for two months, and lived again on 

 remoistening. Forms within the egg were similarly kept for six 

 months. Larvaa remained latent for 2^ years, and might apparently 

 have endured much longer. Sexually mature forms died in a few 

 hours, and could not be resurrected. The age of the larva is an im- 

 portant element in such experiments. The period required for reawaken- 

 ing varies greatly. The temperature of the water used in reviving is 

 likewise important ; raised temperature assists the process. The desicca- 

 tion may be repeated many times ; the author repeated it sixteen times 

 in succession ; each time a longer period was required for revivification ; 

 and after the sixteenth experiment none survived. The process is thus 

 by no means indefinite. The advantage of this power for the species is 

 discussed. Not desiccation alone, but cold also may cause latent life. 

 Some were cooled down to — 19° C, and when the plant in which the 

 worms were, was slowly warmed up again, the Tylenchi larvae revived. 

 If the reheating was sudden, none survived. The cessation of life- 

 activity and the revivification is explained by reference to vital ferments. 

 Lastly, the author notes how putrid substances, of plant or animal 

 origin, or the presence of rotting neighbour Tylenchi may produce the 

 same latent vitality. 



y. Platyhelminthes. 



Taenia nana.t — M. E. Moniez is not inclined to accept without dis- 

 cussion some of the recent results of Prof. Grassi regarding Tsenia nana.% 

 He cannot admit that Cysticercus tenebrionis belongs to that tapeworm, 

 owing to the differences in their spines ; C. tenebrionis appears rather to 

 be the cystic stage of the T. microstoma of the mouse. 



T.murina appears to M. Moniez to be a distinct species from T. nana, 

 for the former is nearly twice the length of the latter, and their embryos 

 are altogether different in form ; moreover, T. murina may be found in 

 localities from which T. nana is altogether absent. 



Some European Triclades.§ — Dr. I. Ijima has notes on various 

 European Planarians, among which Planaria abscissa is a new species, 



* Biol. Centralbl., vii. (1888) pp. 646-59. 



t Comptcs Kcndus, cvi. (1888) pp. 368-70. J This Journal, 1887, p. 961. 



§ Journ. College of Science, Imp. Univ. Japan, i. (1887) pp. 337-58 (1 p].). 



