SCOLECIDA. 
605 
this disease has been greatly exaggerated ; for whilst various 
authors represent the number suffering from hydatid disease at 
from one-seventh to one-fifth of the population, he estimates 
the number of those so affected as to render the disease easily 
recognizable at one-fortieth or one-fiftieth of the inhabitants, 
giving at least 1800 patients in a total population of about 
70,000. Many others attacked by the parasites in a less marked 
degree cannot, of course, be brought into the estimate. The 
Echinococci attack their victims at all ages, and remain in the 
body for many years. 
After explaining the well-known history of the Taniada, the 
author proceeds to account for the enormous prevalence of these 
parasites in Iceland, by statistical details as to the number of 
dogs, sheep, and cattle kept in that island. The number of 
dogs, the hosts of the fully developed Tcjcnia, is so great in Ice- 
land that we may estimate on an average that there is one of 
those animals to every four inhabitants, whilst the sheep and 
cattle together are more than five times as numerous as the 
human population, the sheep alone being in the proportion of 
4*88 to 1. In conclusion, the author recommends certain pro- 
phylactic measures foi" the diminution of the entozootic plague, 
especially the cessation of the practice of giving the viscera of the 
animals killed to the dogs, the avoidance of constant contact with 
the dogs, by keeping them out of doors, and the adoption of some 
means, such as a tax, for restraining the number of dogs within 
moderate bounds. 
SciiNEinEii (/. c. p. 336) proposes the following general 
arrangement of the worms : — 
Nemathelmintha, in which the tegiinientary and muscular tissue of 
the body are separable into two layers : — 
I. The muscles of the body form either a layer of long fibres or two layers, 
an outer, of transverse, and an inner, of longitudinal fibres. In the 
latter case there are always lateral bundles. 
a. Without joints. I. Nematoidea. 2. Chcetognatha. 
h. With joints. 
** Only longitudinal bundles. 3. Gymnotoma^. 
ft With longitudinal and transverse bundles. 4. Chcctopoda. 
II. The muscles of the body forming an outer (longitudinal) and an inner 
(transverse) layer. No lateral bundles. 5. Acanthocephala. 6. Ge- 
phyrea. 
Peatyelmintha, in which the muscular bundles are imbedded in the 
tegumentary tissue. Longitudinal and transverse muscular fibres forming a 
muscular frameworlt. 
’ Schneider (/. c. p. 326) proposes this order for the reception of the genus 
Hhamphoyordius (Kathke), which he states has no aflinities with the Ne- 
mertidae. 
