160 NATURAL SCIENCE [September 1898 



should have an opposite pair of seed-leaves. Gaertuer, who first drew 

 attention to this seedling, considered that the first leaf, to which we 

 have referred, and which grows to a large foliage leaf, is the only- 

 cotyledon. Other botanists have taken the same view, while some 

 maintain that a second cotyledon is developed later. Dr Hildebrand 

 does not consider the nomenclature of these early-developed leaves a 

 matter of importance, but carefully describes what happens. The 

 development of the second leaf, presumably the second cotyledon, may 

 be accelerated by removing the first. The author has had the inesti- 

 mable advantage of observing the life-history of the species from seed 

 to seed, and has been able to make many useful observations which 

 would have been impossible if dried material only had been avail- 

 able. Among others we note an interesting correlation between the 

 duration, or time of appearing, of the leaves and the length of the 

 dormant period before the expiration of which this seed will not 

 germinate. 



The section on variation should be read by all who are interested 

 in this subject, as bearing on the relation between variation and a 

 changing environment. 



The value of Dr Hildebrand's memoir is enhanced by half-a- 

 dozen clear, double-paged plates, containing numerous figures. 



The Female of Heterogyna 



The recently published part 2 of the Transactions of the Entomo- 

 logical Society for the current year contains (pp. 141-150) another 

 of Dr T. A. Chapman's valuable papers on the life-history of Lepi- 

 doptera. He describes the transformations of the South European 

 Heterogyna penella — a small dusky moth with wingless female, often 

 associated with the Psychidae which it resembles, but from its early 

 stages apparently nearer to the Zygaenidae. The vermiform female 

 imago remains attached to the ventral face of the pupa skin. She 

 emerges from her cocoon for pairing, but withdraws into it again 

 after fertilization, becoming replaced exactly in her former position 

 in the pupa as before emergence. Oviposition then begins, and the 

 pupa skin becomes largely filled with eggs, the shrivelled body of 

 the female stopping up the aperture and protecting the eggs against 

 drying up, as well as against insect parasites. Dr Chapman believes 

 that the object of the return of the female into the pupa skin is to 

 ensure this protection for the eggs. And maternal self-sacrifice is 

 carried yet further, for the young caterpillars' first meal is on the 

 remains of their parent. This concluded, they bore through the 

 pupa skin and take to their food-plant. 



