160 K. S. LASHLEY 



into consideration but, believing from observations upon mass 

 cultures that the adult number of tentacles is proportional to 

 the number which the polyps bear when they produce their 

 first buds, she thought herself justified in computing the adult 

 number of tentacles for young poylps which had produced a 

 single bud. Hase concluded that the increase is not regular and 

 that there is no true adult number of tentacles for any polyp. 



Hase further believed that the number of tentacles which 

 the buds have at the time of separation from their parents is not 

 proportional to the number of tentacles which the parents bear 

 at that time. He gave data to show that while the number of 

 tentacles of the parents is increasing with age, that of the suc- 

 cessive offspring of these parents remains constant and does not 

 follow the increase shown by the parents. He also cut a number 

 of polyps into two or three pieces and found that they did not 

 regenerate the same number of tentacles that they had borne 

 originally. From this he concluded: 



Die verschiedene Tentakelzahl ist eine reine Somation und besitzt 

 keinerlei Erblichkeitswert. AIs eine reine Linie (im Sinne von Johann- 

 sen) kann man daher die direkten ungeschlechtlichen Nachkommen 

 einer Hydra nicht bezeichnen. Es ist daher auch nicht moglich char- 

 akteristische Typen zu isolieren und sie erblich konstant zu ei'halten. 

 Aus gleichem Grund kann man auch keine reinen Linien (im vorigen 

 Sinne) aus einer Hydrapopulation durch Selektion sortieren. 



This conclusion is far from justified, however, by the evidence 

 which Hase presents. Records of two parent Hydras are given, 

 which increased slowly in their number of tentacles from five to 

 nine, together with records of all the progeny of each. If the 

 two groups are averaged, as has been done in table 1, it is evident 

 that the buds produced by these two parents after they had 

 acquired a large number of tentacles have a higher average than 

 those produced when the parents had few tentacles. Yet from 

 these data, Hase concludes, ''Wir sehen, zuerst, ein schein- 

 bares Mitgehen der Tentakelzahl der Knospen mit der Mutter, 

 aber bald tritt ein volliger Ruckschlag ein." As I shall show 

 later, this is not true for H. viridis, as it is probably not for H. 

 fusca: the regression is only partial. 



