198 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Nematohelminthes. 



Eggs of Ascaris lumbricoides.* — Lawi-ence D. Wharton has made 

 a study of atypical eggs of this common parasite. Healthy-looking 

 females were placed singly in glass dishes containing Kronecker's solu- 

 tion. This consists of common salt, 6 grms. ; caustic soda, 0"0(j grm. ; 

 distilled water, 1000 c.cm. The solution was changed daily, and a record 

 was kept of the kind of eggs laid by each individual. 



Typical eggs of A. hmibricoides are more or less oval. They average 

 about 70 micra in length and 50 micra in breadth. There is a very 

 thin vitelline membrane, and outside that a thick transparent shell con- 

 sisting of an inner layer of chitin, and an outer layer of some albumi- 

 nous material. The chitinous inner shell is made up of two parts — a 

 thin, tough, very refractive layer, and a thicker, more brittle, outer 

 layer which often shows very delicate striations. The egg does not 

 entirely fill the shell, but forms a ball in the centre with a clear space 

 at each end. The polar bodies are often seen in one of these clear 

 spaces in a newly-laid egg. 



On the outside of the chitinous shell is a thick layer of albuminous 

 material, which is raised all over into small, round, blunt protuberances, 

 producing a very characteristic mammillated appearance. It adheres 

 very tiglitly to the chitinous part of the shell. When the eggs are just 

 laid it is sometimes very soft and sticky, and this accounts for one 

 of the commonest atypical forms found in the fasces. The mammilla- 

 tions are smoothed down and the layer becomes more compact. 



Another common atypical form results from the entire absence 

 of the outer albuminous layer, leaving the perfectly smooth chitinous 

 surface. Such eggs are apt to be mistaken for those of some other 

 worm. The author found that such atypical eggs, which were laid in 

 the dishes, developed normally. The absence of the albumen from the 

 surface must be due to some physiological condition which prevents the 

 formation and deposition of the required substance by the uterine 

 glands. 



Unfertilized ova were also found. They are readily distinguished 

 by the fact that the protoplasm of the egg is not surrounded by a 

 vitelline membrane, and completely fills the shell. The protoplasm 

 is more vacuolated than in the fertilized eggs. The shell may present 

 any of the conditions found in the fertilized eggs. Moreover, some 

 were laid in the dishes without any shell at all. Eggs in this condition 

 would be destroyed in the ffeces. 



Scottish Hairworms.t — James Ritchie gives an account of the 

 occurrence, habits, and characteristics of the Scottish Gordiidaj, with a 

 key for the discrimination of the (five) species recorded from Britain. 

 They occur in ponds, ditches and streams, less frequently among damp 

 vegetation ; they are well known to be marked by their elongated 

 slender shape, tough cuticle, and deep brown colour ; they sometimes 

 occur in groups in an apparently inextricable knot. 



* Philippine Journ. Sci., x. (1915) pp. 110-15. 



t Scottish Naturalist, 1915, pp. 111-5, 136-42, 255-62 (1 pi.). 



