232 SUMMABY OF CURRENT RESEARCHES RELATING TO 



also a fascicle of " podal hooks," which vary not only in corresponding 

 segments of different individuals, but on either side of the segments 

 of the same individual. 



The intestinal canal is a simple median tube dilated in each 

 segment ; the mouth is unarmed, funnel-like, and capacious. There 

 is a well-developed eye on the head at the side of the gullet, but 

 there does not appear to be any trace of posterior terminal eyes, such 

 as are found in Fahricia. The ova appear to be laid and hatched 

 within the tube, so that the young are cared for by the parent till 

 sufficiently developed to provide for themselves. 



The paper concludes with some observations on the species of 

 Fahricia, to which M. speciosa is most closely allied ; the simple eyes 

 were observed to vary in different individuals, and on the different sides 

 of the same individual. 



Parasitic Nematode of the Common Onion.* — J. Chatin describes 

 an apparently new species of Tylenchus, which infests the bulb of the 

 common onion. In its larval stage, it penetrates into and disorganizes 

 the central tissue, converting the fibro-vascular bundles into a brown- 

 ish pultaceous mass. Growth goes on and the sexual organs become 

 matured ; the fertilized ova give rise to claviform larvae, which are 

 able to escape owing to the destruction of the bulb ; these, if the 

 ground is moist enough, wander about on it, but if it is dry they 

 remain quiescent until damp weather comes. They then enter a 

 healthy onion, and the cycle recommences. If the nematoid enters an 

 animal host it passes out with the faeces, and does not undergo in its 

 intestine any further development, nor does it become encysted. On 

 the whole it has a close resemblance to the Anguillula of wheat, but 

 it is not so capable of resisting desiccation. The best remedy against 

 it is to burn all the affected onions. 



New Myzostomata.f — L. Graff gives an account of the new 

 species of Myzostomata which were collected by Dr. P. H. Carpenter 

 off the Crinoids of the ' Hassler ' and ' Blake ' expeditions ; of the 

 22 species, 21 are new ; of those 14 are peculiar to the American col- 

 lections, while the others have been found elsewhere also. Postponing 

 all details to his ' Challenger ' Eeport, the author here merely describes 

 the species, which may be divided into two groups : the members of 

 the first of these are hermaphrodite, ectoparasitic, and produce no 

 deformity on their host ; all but one species are provided with suckers : 

 in the second group the animals have the sexes separate, and live by 

 pairs in cysts of their hosts ; they have no suckers. The entopara- 

 sitic forms produce various abnormalities, merely widening the 

 pinnulae, or at the same time converting them into a spiral coil, or 

 they produce pyriform outgrowths of the pinnules, or various kinds 

 of cavities in the arms. Cysts are sometimes formed by calcareous 

 deposits, which are found on the arms as well as on the disk. 



Bucephalus and Gasterostomum.]: — H. E. Ziegler gives an account 

 of these two parasites. After an historical review and an account of the 



* Comptes Eendus, xcvii. (1883) pp. 1503-5, 



t Bull. Mus. Comp. Zool., xi. (1883) pp. 125-33. 



X Zeitschr. f. Wiss. Zool., xxxix. (1883) pp. 537-71. (2 pis.). 



