26 SUMMARY OF CURRENT RE8E \ RCB i;s RELATING 



Harrison »ives a general account of the hybrids he has produced, soine 



with pure species as parents (primary hybrids), and some with either of 

 i lie two parents a primary hybrid (secondary hybrids). Thus Lycia 

 hirtaria $ x Pcecilnpsis [inuionaria 9 gives a primary hybrid, L. hybr. 

 pilzii ; while Pcecilopsia pomonaria £ x L. hybr. pilzii 9 gives a. 

 secondary hybrid /'. hybr. brooJcsi. One tertiary hybrid has been 

 obtained. 



Harrison calls attention to a number of interesting points, such as 

 the great constitutional strength of the larvae and the growing sterility 

 of the primary hybrids as the specific divergence between the parents 

 increases. The "strength" behaves as a Mendelian dominant, and, 

 granting the possibility of aberrations (mutations) possessing great con- 

 stitutional strength, these two factors alone would result, in some cases, 

 in what could only be classed as new species. 



Characters derived from the undoubtedly weaker Ithysise may be 

 dominant, which may be due to the primitiveness of the genus. The 

 male parent has almost always the superior influence in the hybridization. 

 No reasonable explanation of this fact has ever been suggested. Four 

 of the hybrids exist only in the male sex under normal conditions ; five 

 of the hybrids have the two sexes in approximately equal numbers ; three 

 of the hybrids have a large excess of females. The only form reared 

 from a hybrid female (Lycia hybr. pilzii), namely P&cilopsis hybr. 

 brooksi, was represented by specimens which were hopelessly gynandro- 

 morphic, wings, body, genitalia, antennas being built up of parts chosen 

 at random, as it were, from both sexes of the parents and grand-parents 

 It is worthy of note that the larger and more robust the specimen, 

 the more the male characters predominate, and vice versa. The hybrids 

 have a tendency to emerge long before the parent species. The hybrid 

 females, when produced, vary greatly in their wing development. 



Doncaster draws some general conclusions from his observations on 

 the gametogenesis. There are 28 somatic chromosomes in Lycia hirtaria, 

 giving 13 in the spermatocytes, one of the thirteen being a large one 

 united to a small one. In lthysia zonaria there are 112 somatic and 56 

 spermatocyte chromosomes, which are much smaller than most of those 

 of Lycia hirtaria. The spermatogonial number of the hybrids, which- 

 ever way the cross is made, is as nearly as can be counted 70, of which 

 fourteen are conspicuously larger. Of these fourteen, twelve are derived 

 from the L. hirtaria parent and the other two from the lthysia zonaria 

 parent. The early synapsis stage of the spireme in the young spermato- 

 cytes and oocytes of the hybrids does not differ greatly from that of the 

 pure species, but it is apparently not followed by a normal pachytene 

 (" bouquet ") sta°'e with thick coiled thread. Comparatively few of the 

 chromosomes are paired in the spermatocyte divisions, so that these have 

 only from 5 to 15 fewer than the somatic number. 



Noteworthy is the difference in the chromosome number in nearly 

 related species. Since there are exactly four times as many chromosomes 

 in /. zonaria as in Lycia hirtaria, and since the lthysia zonaria chromo- 

 somes are so much smaller that the total amount of chromatin, as 

 judged by the size of the resting nuclei, is approximately equal in the 

 two species, it seems a fair inference to suppose that the Lycia hirtaria 



